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WO2024225268A1 - Perovskite compound and method for producing same - Google Patents

Perovskite compound and method for producing same Download PDF

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Publication number
WO2024225268A1
WO2024225268A1 PCT/JP2024/015916 JP2024015916W WO2024225268A1 WO 2024225268 A1 WO2024225268 A1 WO 2024225268A1 JP 2024015916 W JP2024015916 W JP 2024015916W WO 2024225268 A1 WO2024225268 A1 WO 2024225268A1
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Prior art keywords
barium
compound
titanate
barium titanate
calcium
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PCT/JP2024/015916
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French (fr)
Japanese (ja)
Inventor
杉本　賢志
学 末田
文陽 釘田
航大 山田
高志 山本
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堺化学工業株式会社
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Publication of WO2024225268A1 publication Critical patent/WO2024225268A1/en

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  • the present invention relates to a perovskite-type compound and a method for producing the same.
  • Barium calcium titanate is a dielectric material that has been attracting attention as an electronic material that improves the temperature dependency and reliability of the dielectric properties of barium titanate by partially replacing the barium sites of barium titanate with calcium, and is used in multilayer ceramic capacitors.
  • multilayer ceramic capacitors have become thinner, and the technology of forming dielectric sheets has become important. Accordingly, dielectric materials used as raw materials are required to have a higher level of particle size uniformity than before.
  • the CV value standard deviation of particle size/average particle size
  • the barium calcium titanate having an average particle size of 620 nm or 252 nm reported so far does not have a sufficiently low CV value, and there is room for improvement in order to further reduce the CV value of barium calcium titanate having a BET specific surface area of 11 to 60 m 2 /g.
  • the present invention aims to provide barium calcium titanate with high uniformity of particle size.
  • the present inventors have investigated a method for obtaining barium calcium titanate having a high uniformity of particle size, and have found that a barium titanate dispersion prepared from a barium compound and an aqueous titanium compound solution is washed with water to obtain a barium titanate having a molar ratio of barium element to titanium element of less than 1.00, mixed with a calcium salt, heat-treated, and then heated in a solvent to disintegrate the barium calcium titanate, thereby producing barium calcium titanate.
  • a barium source and a titanium source are used so that the barium element to titanium element ratio is a predetermined ratio or more when obtaining the barium titanate dispersion, or the barium titanate concentration in the barium titanate dispersion subjected to the debarium ion treatment is a predetermined concentration or more, and the obtained barium calcium titanate particles have a sufficiently low CV value and excellent dispersibility and sheet smoothness, and have completed the present invention.
  • the above-mentioned production method can also be applied to the production of barium strontium titanate.
  • the barium titanate dispersion may also be referred to as a barium titanate slurry.
  • the present invention is as follows.
  • the following general formula (1) Ba (1-x) A x TiO 3 (1) (In the formula, A represents Ca or Sr, and x is a number satisfying 0.00 ⁇ x ⁇ 0.30), A perovskite compound characterized in that the CV value, which is expressed as the ratio of the standard deviation of particle diameter to the average particle diameter (equivalent circle diameter) obtained by observation with a scanning electron microscope (standard deviation of particle diameter/average particle diameter x 100), is 20% or less.
  • the method for producing a perovskite compound of the present invention is a method for producing barium calcium titanate with high uniformity in particle size, and the barium calcium titanate obtained by this method can be suitably used as a raw material for multilayer ceramic capacitors, etc.
  • 1 is a SEM photograph of a barium titanate precursor slurry having a concentration of 80 g/L obtained in the barium ion removing treatment step in Example 1.
  • 1 is a SEM photograph of the barium calcium titanate obtained in Example 1.
  • 1 is a SEM photograph of a barium titanate precursor slurry having a concentration of 60 g/L obtained in the barium ion removing treatment step of Comparative Example 1.
  • 1 is a SEM photograph of barium calcium titanate obtained in Comparative Example 1.
  • 1 is a HAADF-STEM observation photograph of the barium calcium titanate obtained in Example 1.
  • 1 is a HAADF-STEM observation photograph of the barium calcium titanate obtained in Example 1 (Ba: white, Ti: gray).
  • FIG. 5 is an EDS mapping of the barium calcium titanate obtained in Example 1, performed in the same field of view as in FIG. 4 (Ba: only white is displayed).
  • FIG. 5 is an EDS mapping of the barium calcium titanate obtained in Example 1, performed in the same field of view as in FIG. 4 (Ca: only white is shown). 1 shows the results of XRD measurement of barium calcium titanate obtained in Example 7.
  • the perovskite compound of the present invention is represented by the following general formula (1): Ba (1-x) A x TiO 3 (1) (wherein A represents Ca or Sr, and x is a number satisfying 0.00 ⁇ x ⁇ 0.30), and is characterized in that the CV value, which is expressed as the ratio of the standard deviation of the particle diameter to the average particle diameter (circle-equivalent diameter) obtained by observation with a scanning electron microscope (standard deviation of particle diameter/average particle diameter ⁇ 100), is 20% or less.
  • a perovskite type compound having a high uniformity of particle size a dielectric layer having uniform dielectric properties can be formed, and therefore the compound is suitable as a material for the dielectric layer of a ceramic capacitor.
  • the perovskite type compound of the present invention having a high uniformity of particle size is also characterized by high dispersibility in solvents and resins, and in this respect, the compound is also suitable as a material for forming the dielectric layer of a ceramic capacitor by mixing with a resin or the like.
  • the CV value of the perovskite compound of the present invention may be 20% or less, and is preferably 19% or less, more preferably 18.5% or less, even more preferably 18% or less, particularly preferably 17.5% or less, particularly preferably 17% or less, and most preferably 16% or less.
  • the CV value of the perovskite compound can be measured by the method described in the Examples below.
  • the perovskite compound of the present invention preferably has a BET specific surface area of 5 to 70 m 2 /g. Small particles having such a BET specific surface area are more suitable for electronic material applications such as multilayer ceramic capacitors. Furthermore, in order to reduce re-aggregated components in the dispersion step and facilitate dispersion, a small BET specific surface area is preferable.
  • the BET specific surface area of the perovskite compound is more preferably 8 to 35 m 2 /g, even more preferably 10 to 30 m 2 /g, and most preferably 15 to 25 m 2 /g.
  • the BET specific surface area of the perovskite compound can be measured by the method described in the Examples below.
  • the perovskite compound of the present invention preferably has an average particle size of 10 to 210 nm. With such an average particle size, dispersion and handling are easy when forming a dielectric layer, and a uniform dielectric layer can be formed.
  • the average particle size is more preferably 20 to 160 nm, even more preferably 30 to 150 nm, particularly preferably 35 to 130 nm, particularly preferably 40 to 100 nm, and most preferably 45 to 60 nm.
  • the average particle size of the perovskite compound can be measured by the method described in the Examples below.
  • the perovskite compound of the present invention preferably has a particle circularity of 0.85 or more. With such a circularity, it is easy to prepare a smooth dielectric layer.
  • the circularity is more preferably 0.90 or more, and even more preferably 0.95 or more.
  • the circularity of the perovskite compound particles can be measured by the method described in the Examples below.
  • the arithmetic mean roughness (Ra) of the surface is preferably 0.110 ⁇ m or less, more preferably 0.095 ⁇ m or less, even more preferably 0.080 ⁇ m or less, and particularly preferably 0.070 ⁇ m or less.
  • the maximum height Rz is preferably 1.400 ⁇ m or less, more preferably 1.200 ⁇ m or less, even more preferably 0.085 ⁇ m or less, and particularly preferably 0.080 ⁇ m or less. With such an arithmetic mean roughness and maximum height, it is easy to produce a smooth surface.
  • the method for producing a film assuming a green sheet using particles of a perovskite compound, and the arithmetic mean roughness and maximum height of the produced film are as described in the examples below. In this way, when a film equivalent to a green sheet is produced using the particles of the present invention, it is possible to obtain a very smooth surface.
  • the perovskite type compound represented by the above general formula (1) includes both those in which x in general formula (1) is a number in the range of 0.00 ⁇ x ⁇ 0.30 and the amount of calcium or strontium dissolved in solid solution is small, where x is a number in the range of 0.00 ⁇ x ⁇ 0.15, and those in which the amount of calcium or strontium dissolved in solid solution is large, where x is a number in the range of 0.15 ⁇ x ⁇ 0.30, but it is preferable that x is 0.005 ⁇ x ⁇ 0.05, and more preferably 0.01 ⁇ x ⁇ 0.03.
  • Perovskite compounds with a small amount of calcium or strontium dissolved are considered to be suitable for consumer capacitors (such as smartphones and tablets) that require a balance between small size, high capacity, and improved reliability, such as excellent temperature characteristics and reliability while maintaining high ferroelectricity, among other multilayer ceramic capacitors.
  • perovskite compounds with a large amount of calcium or strontium dissolved, where x is a number of 0.15 ⁇ x ⁇ 0.30 are considered to be suitable for automotive capacitors that require heat resistance at higher temperatures, as the increased amount of solid solution further improves temperature characteristics.
  • the manufacturing method of the perovskite compound of the present invention uses a manufacturing method including a barium titanate dispersion preparation step of mixing a barium compound with an aqueous titanium compound solution to obtain a barium titanate dispersion, a barium ion de-ionization treatment step of washing the barium titanate dispersion obtained in the barium titanate dispersion preparation step to obtain barium titanate having a molar ratio of barium element to titanium element of less than 1.00, a heat treatment step of mixing the barium titanate obtained in the barium ion de-ionization treatment step with a calcium salt or a strontium salt and subjecting the mixture to heat treatment, and a disintegration step of heating the compound obtained in the heat treatment step in a solvent to disintegrate the compound.
  • the manufacturing method is characterized in that in the barium titanate dispersion preparation step, a barium compound and an aqueous titanium compound solution are used so that the molar ratio (Ba/Ti) of the barium element in the barium compound to the titanium element in the aqueous titanium compound solution is 4.5 or more (hereinafter also referred to as the first condition), or the barium titanate concentration in the barium titanate dispersion used in the barium ion debarium treatment step is 65 g/L or more (hereinafter also referred to as the second condition).
  • the barium titanate dispersion preparation step is a step of preparing a barium titanate dispersion that is a precursor of the desired barium calcium titanate or barium strontium titanate.
  • the precursor barium titanate dispersion is prepared in a state in which a certain amount of barium ions are present in the system, and this allows a barium titanate slurry with little aggregation to be obtained. Then, if barium calcium titanate or barium strontium titanate is produced by carrying out the barium ion removal process and the disintegration process using such a barium titanate slurry with little aggregation as a precursor, barium calcium titanate or barium strontium titanate with high uniformity in particle size can be obtained.
  • the second step is carried out in such a manner that a certain amount of barium ions are present in the dispersion liquid, and in this manner, barium calcium titanate or barium strontium titanate having a high degree of particle size uniformity can be obtained.
  • the molar ratio of barium element to titanium element may be 4.5 or more, and is preferably 5 or more, and more preferably 6 or more.
  • the molar ratio of barium element to titanium element is preferably 10 or less.
  • the number of moles of barium element in the barium compound relative to the number of moles of titanium element in the titanium compound aqueous solution may be less than 5, but considering the efficiency of preparation of barium titanate, it is preferable to use the titanium compound aqueous solution and the barium compound so that the ratio is 0.5 or more.
  • the barium compound used in the barium titanate dispersion preparation step is not particularly limited, but may be barium hydroxide, barium oxalate, barium acetate, barium nitrate, barium nitrite, barium chloride, barium chlorate, barium perchlorate, barium bromide, barium bromate, barium iodide, barium hydrogen phosphate, barium nitride, barium oxide, barium peroxide, barium sulfide, barium azide, barium fluoride, barium formate, barium lactate, barium metaphosphate, barium methacrylate, barium rhodizonate, barium tartrate, barium sulfate, barium sulfite, barium trifluoromethanesulfonate, bis(acetylacetonato)diaquabarium(II), barium benzoate, barium 2-ethylhexanoate, barium octan
  • the titanium compound aqueous solution used in the barium titanate dispersion preparation step includes an aqueous solution of titanium tetrachloride, a water-soluble titanium complex, etc., and one or more of these can be used.
  • the ligand of the water-soluble titanium complex preferably contains a hydroxy acid (salt).
  • the hydroxy acid may be an ⁇ -hydroxy acid.
  • the ⁇ -hydroxy acid includes, for example, glycolic acid, citric acid, malic acid, tartaric acid, lactic acid, etc.
  • the titanium complex may contain an ammonium salt of lactic acid as a ligand.
  • titanium bis(ammonium lactate) dihydroxide (TALH) can be mentioned.
  • an aqueous solution of titanium tetrachloride and an aqueous solution of TALH are preferred, and an aqueous solution of titanium tetrachloride is more preferred.
  • the barium compound When mixing with the aqueous titanium compound solution in the above-mentioned barium titanate dispersion preparation process, the barium compound may be mixed as a solid, but in order to produce a sufficient amount of barium titanate, it is preferable to mix it after making it into a solution.
  • the solvent used to prepare the barium compound solution may be either an organic solvent or an inorganic solvent, but may be water or a water-miscible organic solvent such as methanol or ethanol, and one or more of these may be used. Among these, it is preferable to use water or a mixture of a water-miscible organic solvent and water.
  • both the barium compound and the aqueous titanium compound solution may be added to a container, or one may be added to the other.
  • the amount of the solvent used in the barium titanate dispersion preparation step is not particularly limited, but is preferably an amount that results in a solids concentration in the resulting barium titanate dispersion of 10 to 1000 g/L, more preferably 10 to 500 g/L, even more preferably 10 to 250 g/L, and most preferably 10 to 100 g/L. If the solids concentration is too low, the productivity of the perovskite compound decreases, and if the solids concentration is too high, there is a risk of the washing treatment in the barium ion removal treatment step becoming non-uniform.
  • the amount of the solvent used here refers to the total amount of water contained in the aqueous titanium compound solution and the solvent contained in the barium compound solution when the barium compound is mixed in the form of a solution.
  • the pH of the mixed solution of the barium compound and the aqueous titanium compound solution it is preferable to adjust the pH of the mixed solution of the barium compound and the aqueous titanium compound solution to 5 or more. By mixing in such an alkaline range, a sufficient amount of barium titanate can be produced.
  • the pH of the mixed solution of the barium compound and the aqueous titanium compound solution is more preferably 8 or more, and even more preferably 10 or more.
  • the barium titanate concentration in the barium titanate dispersion may be 65 g/L or more, preferably 80 g/L or more, and more preferably 110 g/L or more.
  • the barium titanate concentration in the barium titanate dispersion liquid used in the barium ion removal treatment step may be less than 65 g/L, but considering the efficiency of producing the perovskite compound, it is preferable that it is 10 g/L or more.
  • the barium ion removing treatment step it is only necessary to subject the barium titanate dispersion obtained in the barium titanate dispersion preparation step to a washing treatment so that the molar ratio of barium element to titanium element is less than 1.00.
  • the molar ratio of barium element to titanium element can be confirmed by X-ray fluorescence analysis (XRF).
  • the barium titanate is washed in the barium ion removing process to efficiently dissolve barium ions from the barium titanate.
  • the washing process may be any process capable of making the molar ratio of barium element to titanium element less than 1.00, and is preferably carried out by adding an acid while stirring the barium titanate slurry.
  • the barium ion removal treatment is preferably carried out by a washing treatment using an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, or an organic acid such as acetic acid, oxalic acid, or citric acid.
  • the treatment to make the molar ratio of barium element to titanium element less than 1.00 can be carried out by washing with water, but this is not practical because it requires a huge amount of water. Instead, it is quantitative to elute barium ions using an acid, and this is suitable for industrial production.
  • the method of debarium ion treatment in the above-mentioned debarium ion treatment step is not particularly limited as long as the molar ratio of barium element to titanium element of barium titanate can be less than 1.00, but it is preferable to add an acid to barium titanate and perform the treatment so that the pH of the obtained slurry is 5 to 11. It is also preferable to appropriately adjust the pH of the slurry within the above-mentioned pH range depending on the specific surface area of the barium titanate to be debarium ion treated in the debarium ion treatment step and the amount of barium element substituted with calcium element or strontium element.
  • the molar ratio of barium element is about 0.60 to 0.70
  • the molar ratio is about 0.75 to 0.90.
  • washing is preferably performed until the electrical conductivity of the washing water is 100 ⁇ S/cm or less. More preferably, it is 50 ⁇ S/cm or less.
  • the heat treatment step is a step in which the barium titanate obtained in the barium ion removal treatment step is mixed with a calcium salt or a strontium salt, and the mixture is subjected to a heat treatment.
  • the calcium salt and strontium salt to be mixed with barium titanate are not particularly limited, and examples thereof include calcium and strontium oxides, hydroxides, chlorides, carbonates, sulfates, nitrates, phosphates, and organic acid salts such as hydroiodic acid, acetates, oxalates, and citric acid, and one or more of these can be used.
  • the amount of calcium salt used is preferably such that the amount of calcium element contained in the calcium salt is more than 0 mol% and 30 mol% or less relative to 100 mol% of titanium element contained in barium titanate.
  • the amount of calcium salt used is more preferably such that the amount of calcium element contained in the calcium salt is 0.5 to 20 mol% relative to 100 mol% of titanium element contained in barium titanate, and even more preferably such that the amount of calcium element is 1 to 10 mol%.
  • strontium salt When a strontium salt is used in the heat treatment step, it is also preferable to use the strontium salt so that the amount of elemental strontium contained in the strontium salt is in the same ratio as above relative to 100 mol % of elemental titanium contained in barium titanate.
  • a barium salt may be further mixed with the barium titanate.
  • the behavior of the perovskite compound during the heat treatment can be controlled, and the particle size can be controlled.
  • the amount of the barium salt used can be appropriately determined depending on the desired particle size, etc.
  • the method for mixing barium titanate with a calcium salt or a strontium salt is not particularly limited as long as they are thoroughly mixed, but an example of this is adding a calcium salt or a strontium salt to a barium titanate slurry and then stirring the slurry with a stirrer or the like. The same method is used for mixing the barium salt.
  • the temperature for heat treating the mixture of barium titanate and a calcium salt or a strontium salt is preferably 400 to 1200° C., more preferably 450 to 1000° C., even more preferably 500 to 800° C., and particularly preferably 550 to 700° C.
  • the heat treatment time is preferably 0.5 to 12 hours, more preferably 1 to 10 hours, and even more preferably 2 to 8 hours.
  • the atmosphere in which the heat treatment is carried out is not particularly limited, and may be air or an inert gas atmosphere such as nitrogen or argon.
  • the number of times of heat treatment in the heat treatment step is not particularly limited, and may be one or more times.
  • the barium titanate obtained in the barium ion removing treatment step is mixed with a calcium salt or a strontium salt, heated and dried to obtain a dry mixture, and then the dry mixture is fired.
  • a calcium salt or a strontium salt By drying a mixture of barium titanate and a calcium salt or a strontium salt before firing, it is possible to suppress segregation of the composition and obtain a precursor in which calcium and strontium elements are uniformly distributed.
  • firing such a precursor calcium and strontium elements are uniformly dissolved in the perovskite compound, and the uniformity of the particles is improved.
  • the method for drying the mixture is not particularly limited, but a method using any one of a tray dryer, a fluidized bed dryer, an airflow dryer, and a spray dryer is preferred.
  • a method using any one of a tray dryer, a fluidized bed dryer, an airflow dryer, and a spray dryer is preferred.
  • the process of mixing the barium titanate obtained in the barium ion removal treatment process with a calcium salt or a strontium salt and heating and drying to obtain a dry mixture is also referred to as the drying process
  • the process of firing the dry mixture is also referred to as the firing process.
  • the temperature and time for firing the dried mixture are preferably the same as those for the heat treatment step.
  • the mixture is preferably dried at 80 to 300° C. in the drying step, and more preferably at 90 to 110° C.
  • the time for drying the mixture is preferably 0.5 to 24 hours, more preferably 2 to 6 hours, in the case of a tray dryer.
  • the method for producing a perovskite compound of the present invention further includes a disintegration step of heating the perovskite compound obtained in the heat treatment step in a solvent to disintegrate the particles, thereby obtaining a perovskite compound with few connections between particles.
  • the heating temperature when the perovskite compound is heated in a solvent to disintegrate in the disintegration step is not particularly limited as long as the particles of the perovskite compound are disintegrated, but is preferably 30 to 500 ° C.
  • the aggregated particles of the perovskite compound can be sufficiently disintegrated, and a perovskite compound having few connections between particles and a high proportion of particles that are close to spherical can be obtained.
  • the temperature at which the perovskite compound is heated is preferably 30 to 500 ° C., but is more preferably 60 to 300 ° C. from the viewpoint of more sufficiently disintegrating the aggregated particles of the perovskite compound. More preferably, it is 100 to 200 ° C., and particularly preferably, it is 100 to 180 ° C.
  • the time for heating the perovskite compound in the disintegration step is not particularly limited, but is preferably 1 to 120 hours from the viewpoint of sufficiently disintegrating aggregated particles of the perovskite compound. More preferably, it is 2 to 72 hours, even more preferably, it is 4 to 60 hours, and particularly preferably, it is 10 to 40 hours. Depending on the desired properties, it may be 10 to 30 hours in consideration of production efficiency.
  • the atmosphere in which the heating is performed is not particularly limited, and may be air or an inert gas atmosphere such as nitrogen or argon.
  • the solvent used when heating the perovskite compound in the above-mentioned disintegration step may be either an organic solvent or an inorganic solvent, but examples of the solvent include water and water-miscible organic solvents such as methanol and ethanol, and one or more of these can be used. Among these, it is preferable to use water or a mixture of a water-miscible organic solvent and water.
  • the disintegration step may be carried out by adding an acid or a base, or a substance that acts as an acid or a base in the solvent, to the solvent. By adding these to the solvent, the aggregated particles can be disintegrated more efficiently.
  • the acid may be the same as that used in the barium ion removal treatment in the barium ion removal treatment step.
  • the base include inorganic bases such as hydroxides of alkali metals or alkaline earth metals, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and barium hydroxide, and organic bases such as organic amines. Among these, it is preferable to use barium hydroxide because of its high effect of deagglomerating aggregated particles of the perovskite compound.
  • the acids and bases, or those which act as acids and bases in a solvent may each be used alone or in combination of two or more.
  • the method for producing a perovskite compound of the present invention may include other steps in addition to the steps described above.
  • Examples of the other steps include a step of dispersing or washing the perovskite compound obtained in the heat treatment step or the disintegration step, and a step of drying the washed perovskite compound.
  • the dispersion method in the step of dispersing the perovskite compound is not particularly limited, but examples thereof include a method using a disperser using media such as a bead mill, or a media-less disperser such as an emulsifier or an ultrasonic disperser.
  • the washing method in the step of washing the perovskite compound is not particularly limited, but washing with water is preferred.
  • the drying method in the step of drying the washed perovskite compound is not particularly limited, and any one of a box dryer, a fluidized bed dryer, an air flow dryer, and a spray dryer may be used.
  • a box dryer a method in which the compound is allowed to stand in an atmosphere at 80 to 300° C. for 0.5 to 24 hours may be mentioned.
  • the method for producing the perovskite compound of the present invention is a method capable of producing barium calcium titanate having a high degree of uniformity in particle size, and the barium calcium titanate, which is one type of perovskite compound of the present invention and is obtained by the method for producing the perovskite compound of the present invention, can be suitably used for electronic material applications such as multilayer ceramic capacitors.
  • composition Analysis The composition was analyzed using an X-ray fluorescence analyzer (ZSX Primus II, manufactured by Rigaku Corporation, calibration curve method) to determine the molar ratios of Ba/Ti, Ca/Ti, and (Ba+Ca)/Ti.
  • X-ray fluorescence analyzer ZSX Primus II, manufactured by Rigaku Corporation, calibration curve method
  • Specific surface area The specific surface areas of the barium titanate powder and barium calcium titanate powder were measured by a BET single point method using a fully automatic specific surface area measuring device (Macsorb HM model-1220 manufactured by Mountec Co., Ltd.) after degassing at 350° C. for 15 minutes.
  • the surface roughness of this film was measured with a surface roughness meter.
  • the surface roughness was measured using a SURFCOM 130A (manufactured by Tokyo Seimitsu Co., Ltd.).
  • Example 1 Barium titanate dispersion preparation process
  • a 5-L reaction vessel was charged with 1.3 L of pure water and 1,157 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.), and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution.
  • barium ion removal process While stirring the barium titanate precursor slurry with a stirrer, a nitric acid aqueous solution with a concentration of 20% was dropped, the pH of the slurry was adjusted to 11.0, and the pH was maintained for 1 hour. After this, the mixture was filtered and washed with water until the electrical conductivity of the filtrate was 50 ⁇ S/cm or less, and a cake was obtained after washing with water. Water was added to the cake to make the liquid volume 1 L, and after washing with water, a barium titanate bulk slurry was obtained.
  • Examples 2 to 7 Example 2 to 7 were carried out in the same manner as Example 1, except that the types and amounts of various components used in the reaction and the reaction conditions were changed as shown in Table 1.
  • the results of XRD measurement of the barium calcium titanate obtained in Example 7 are shown in FIG. No phase was observed in the XRD measurement chart of FIG. 7, confirming that a highly pure perovskite type compound was obtained.
  • Comparative Example 1 A 5-L reaction vessel was charged with 1.6 L of pure water and 868 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.), and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution. 0.17 L of titanium tetrachloride solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., Ti equivalent concentration 186 g/L) was mixed with the above barium hydroxide aqueous solution to obtain a barium titanate precursor aqueous slurry with a concentration of 60 g/L in terms of BaTiO 3.
  • the Ba/Ti molar ratio at the end of mixing the barium hydroxide aqueous solution and the titanium tetrachloride solution was 4.0.
  • the results of SEM observation of the obtained barium titanate precursor aqueous slurry are shown in Fig. 2-1. In Fig. 2-1, it was confirmed that particles of the barium titanate precursor were aggregated in the area surrounded by a solid line. Thereafter, the same procedures as in Example 1 were carried out up to the deagglomeration step, except that each step was changed as shown in Table 1, to obtain a barium calcium titanate powder of Comparative Example 1.
  • the results of SEM observation of the barium calcium titanate obtained in the deagglomeration process are shown in Figure 2-2. In Figure 2-2, coarse particles of barium calcium titanate were observed in the area surrounded by a solid line, and it was confirmed that the particle size varied.
  • Comparative Examples 2 to 3 Comparative Examples 2 and 3 were carried out in the same manner as Comparative Example 1, except that the types and amounts of the components used in the reaction and the reaction conditions were changed as shown in Table 1.
  • Comparative Example 4 Barium titanate dispersion preparation process 2.1 L of pure water and 909 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.) were placed in a 5 L reaction vessel and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution.
  • aqueous titanium hydroxide slurry manufactured by Sakai Chemical Industry Co., Ltd., concentration of 184 g/L calculated as Ti
  • concentration of 184 g/L calculated as Ti 0.50 L was mixed with the above aqueous barium hydroxide solution to obtain an aqueous barium titanate slurry having a concentration of 159 g/L calculated as BaTiO3.
  • the Ba/Ti molar ratio was 2.2 when the aqueous titanium hydroxide slurry was added to the aqueous barium hydroxide solution.
  • the above barium titanate water slurry was placed in an autoclave vessel and subjected to hydrothermal treatment for 6 hours at 100° C.
  • the contents of the autoclave were allowed to cool to room temperature to obtain a barium titanate precursor slurry.
  • Barium ion removal process While stirring the barium titanate precursor slurry with a stirrer, a nitric acid aqueous solution with a concentration of 20% was dropped to adjust the slurry pH to 7.0, and the pH was maintained for 1 hour. After this, the mixture was filtered and washed with water until the electrical conductivity of the filtrate was 100 ⁇ S/cm or less, and a cake was obtained after washing with water. Water was added to the cake to make the liquid volume 1 L, and a barium titanate precursor slurry was obtained after washing with water.
  • Comparative Example 5 Comparative Example 5 was carried out in the same manner as Comparative Example 4, except that the types and amounts of the components used in the reaction and the reaction conditions were changed as shown in Table 1.
  • barium calcium titanate having a CV value of 20% or less was obtained in all of Examples 1 to 7.
  • the barium calcium titanate obtained in Comparative Examples 1 to 5 all had a CV value of more than 20%. From these results, it was confirmed that by using the method for producing a perovskite compound of the present invention, barium calcium titanate having a high uniformity in particle size can be obtained.

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Abstract

The present invention provides barium calcium titanate which has high uniformity of particle size. The present invention provides a perovskite compound which is characterized by being represented by general formula (1) Ba(1-x)AxTiO3 (wherein A represents Ca or Sr, and x is a number that satisfies 0.00 < x ≤ 0.30), and which is also characterized in that the CV value expressed by the ratio ((standard deviation of particle diameter)/(average particle diameter) × 100) of the standard deviation of particle diameter to the average particle diameter (circle-equivalent diameter) as determined by the observation with a scanning electronic microscope is 20% or less.

Description

ペロブスカイト型化合物及びその製造方法Perovskite compound and method for producing same
本発明は、ペロブスカイト型化合物及びその製造方法に関する。 The present invention relates to a perovskite-type compound and a method for producing the same.
チタン酸バリウムカルシウムは誘電体材料の１つであり、チタン酸バリウムのバリウムサイトを一部カルシウムに置換することで、チタン酸バリウムの誘電特性の温度依存性や信頼性を改善した電子材料として注目され、積層セラミックコンデンサ用途で使用されている。近年、積層セラミックスコンデンサの薄層化が進んでおり、誘電体をシート形成する技術が重要視されている。これに伴い、原料として用いられる誘電体材料には従来よりも高いレベルの粒子サイズの均一性が求められるようになってきている。
粒子サイズの均一性を示すパラメータとして、ＣＶ値（粒子径の標準偏差／平均粒子径）が知られている。チタン酸バリウムカルシウムはその多くが高温の熱処理工程を経て作られていることから、粒子径が揃ったものを得ることは難しいのが現状である。従来のチタン酸バリウムカルシウムとして、平均粒子径が６２０ｎｍや２５２ｎｍのチタン酸バリウムカルシウムが報告されており（特許文献１、２参照）、そのＣＶ値はそれぞれ２２％と２１％である。またＢＥＴ比表面積が１１～６０ｍ２／ｇのチタン酸バリウムカルシウムが報告されている（特許文献３参照）。 Barium calcium titanate is a dielectric material that has been attracting attention as an electronic material that improves the temperature dependency and reliability of the dielectric properties of barium titanate by partially replacing the barium sites of barium titanate with calcium, and is used in multilayer ceramic capacitors. In recent years, multilayer ceramic capacitors have become thinner, and the technology of forming dielectric sheets has become important. Accordingly, dielectric materials used as raw materials are required to have a higher level of particle size uniformity than before.
The CV value (standard deviation of particle size/average particle size) is known as a parameter indicating the uniformity of particle size. Since most barium calcium titanate is produced through a high-temperature heat treatment process, it is currently difficult to obtain barium calcium titanate with a uniform particle size. Conventional barium calcium titanate with average particle sizes of 620 nm and 252 nm has been reported (see Patent Documents 1 and 2), and the CV values are 22% and 21%, respectively. Also, barium calcium titanate with a BET specific surface area of 11 to 60 m 2 /g has been reported (see Patent Document 3).
特許第４２５６１１７号公報Patent No. 4256117 特許第４５２５７８８号公報Patent No. 4525788 特許第６９５４５０１号公報Patent No. 6954501
上述のとおり、これまでに報告されている平均粒子径が６２０ｎｍや２５２ｎｍのチタン酸バリウムカルシウムはＣＶ値が十分に低いものではなく、ＢＥＴ比表面積が１１～６０ｍ２／ｇのチタン酸バリウムカルシウムについてもＣＶ値を更に低いものとする改善の余地がある。 As described above, the barium calcium titanate having an average particle size of 620 nm or 252 nm reported so far does not have a sufficiently low CV value, and there is room for improvement in order to further reduce the CV value of barium calcium titanate having a BET specific surface area of 11 to 60 m 2 /g.
本発明は、上記現状に鑑み、粒子サイズの均一性が高いチタン酸バリウムカルシウムを提供することを目的とする。 In view of the above-mentioned current situation, the present invention aims to provide barium calcium titanate with high uniformity of particle size.
本発明者らは、粒子サイズの均一性が高いチタン酸バリウムカルシウムを得る方法について検討し、バリウム化合物とチタン化合物水溶液を原料として調製したチタン酸バリウム分散液を水洗処理してチタン元素に対するバリウム元素のモル比を１．００未満としたチタン酸バリウムとカルシウム塩とを混合し、熱処理した後、チタン酸バリウムカルシウムを溶媒中で加熱して解粒することでチタン酸バリウムカルシウムを製造する方法を用い、この方法においてチタン酸バリウム分散液を得る際にチタン元素に対するバリウム元素が所定の割合以上となるようにバリウム源とチタン源を使用するか、脱バリウムイオン処理に供するチタン酸バリウム分散液中のチタン酸バリウム濃度を所定の濃度以上とすることで、得られたチタン酸バリウムカルシウム粒子は十分にＣＶ値が低く、分散性やシート平滑性に優れることを見出し、本発明を完成するに至った。上述の製造方法は、チタン酸バリウムストロンチウムの製造にも適用可能である。なお、チタン酸バリウム分散液はチタン酸バリウムスラリーとも表記することがある。 The present inventors have investigated a method for obtaining barium calcium titanate having a high uniformity of particle size, and have found that a barium titanate dispersion prepared from a barium compound and an aqueous titanium compound solution is washed with water to obtain a barium titanate having a molar ratio of barium element to titanium element of less than 1.00, mixed with a calcium salt, heat-treated, and then heated in a solvent to disintegrate the barium calcium titanate, thereby producing barium calcium titanate. In this method, a barium source and a titanium source are used so that the barium element to titanium element ratio is a predetermined ratio or more when obtaining the barium titanate dispersion, or the barium titanate concentration in the barium titanate dispersion subjected to the debarium ion treatment is a predetermined concentration or more, and the obtained barium calcium titanate particles have a sufficiently low CV value and excellent dispersibility and sheet smoothness, and have completed the present invention. The above-mentioned production method can also be applied to the production of barium strontium titanate. The barium titanate dispersion may also be referred to as a barium titanate slurry.
すなわち本発明は、以下のとおりである。
［１］下記一般式（１）：
Ｂａ（１－ｘ）ＡｘＴｉＯ３　　　（１）
（式中、ＡはＣａ又はＳｒを表す。ｘは、０．００＜ｘ≦０．３０の数である。）で表され、
走査電子顕微鏡観察から得られる平均粒子径（円相当径）に対する粒子径の標準偏差の割合（粒子径の標準偏差／平均粒子径×１００）で表されるＣＶ値が２０％以下であることを特徴とするペロブスカイト型化合物。 That is, the present invention is as follows.
[1] The following general formula (1):
Ba (1-x) A x TiO 3 (1)
(In the formula, A represents Ca or Sr, and x is a number satisfying 0.00<x≦0.30),
A perovskite compound characterized in that the CV value, which is expressed as the ratio of the standard deviation of particle diameter to the average particle diameter (equivalent circle diameter) obtained by observation with a scanning electron microscope (standard deviation of particle diameter/average particle diameter x 100), is 20% or less.
［２］ＢＥＴ比表面積が５～７０ｍ２／ｇであることを特徴とする［１］に記載のペロブスカイト型化合物。 [2] The perovskite compound according to [1], characterized in that the BET specific surface area is 5 to 70 m 2 /g.
［３］バリウム化合物とチタン化合物水溶液とを混合してチタン酸バリウム分散液を得るチタン酸バリウム分散液調製工程と、
チタン酸バリウム分散液調製工程で得られたチタン酸バリウム分散液を洗浄処理してチタン元素に対するバリウム元素のモル比が１．００未満であるチタン酸バリウムを得る脱バリウムイオン処理工程と、
脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、熱処理する熱処理工程と、
熱処理工程で得られた化合物を溶媒中で加熱して解粒する解粒工程とを含み、
チタン酸バリウム分散液調製工程において、バリウム化合物中のバリウム元素とチタン化合物水溶液中のチタン元素とのモル比（Ｂａ／Ｔｉ）が４．５以上となるようにバリウム化合物とチタン化合物水溶液とを用いるか、脱バリウムイオン処理工程に用いるチタン酸バリウム分散液中のチタン酸バリウム濃度を６５ｇ／Ｌ以上とするかの少なくとも一方を行う
ことを特徴とするペロブスカイト型化合物の製造方法。 [3] A barium titanate dispersion preparation step of mixing a barium compound and an aqueous titanium compound solution to obtain a barium titanate dispersion;
a barium ion removing process for washing the barium titanate dispersion obtained in the barium titanate dispersion preparation process to obtain barium titanate having a molar ratio of barium element to titanium element of less than 1.00;
a heat treatment step of mixing the barium titanate obtained in the barium ion removing treatment step with a calcium salt or a strontium salt and heat treating the mixture;
A disintegration step of heating the compound obtained in the heat treatment step in a solvent to disintegrate the compound,
A method for producing a perovskite compound, characterized in that in a barium titanate dispersion preparation step, a barium compound and an aqueous titanium compound solution are used so that the molar ratio (Ba/Ti) of the barium element in the barium compound to the titanium element in the aqueous titanium compound solution is 4.5 or more, or the barium titanate concentration in the barium titanate dispersion used in the barium ion debarium treatment step is 65 g/L or more.
本発明のペロブスカイト型化合物の製造方法は、粒子サイズの均一性が高いチタン酸バリウムカルシウムを製造することができる方法であり、この製造方法で得られたチタン酸バリウムカルシウムは、積層セラミックスコンデンサ等の原料として好適に用いることができる。 The method for producing a perovskite compound of the present invention is a method for producing barium calcium titanate with high uniformity in particle size, and the barium calcium titanate obtained by this method can be suitably used as a raw material for multilayer ceramic capacitors, etc.
実施例１の脱バリウムイオン処理工程で得られた８０ｇ／Ｌ濃度のチタン酸バリウム前駆体スラリーのＳＥＭ観察写真である。1 is a SEM photograph of a barium titanate precursor slurry having a concentration of 80 g/L obtained in the barium ion removing treatment step in Example 1. 実施例１で得られたチタン酸バリウムカルシウムのＳＥＭ観察写真である。1 is a SEM photograph of the barium calcium titanate obtained in Example 1. 比較例１の脱バリウムイオン処理工程で得られた６０ｇ／Ｌ濃度のチタン酸バリウム前駆体スラリーのＳＥＭ観察写真である。1 is a SEM photograph of a barium titanate precursor slurry having a concentration of 60 g/L obtained in the barium ion removing treatment step of Comparative Example 1. 比較例１で得られたチタン酸バリウムカルシウムのＳＥＭ観察写真である。1 is a SEM photograph of barium calcium titanate obtained in Comparative Example 1. 実施例１で得られたチタン酸バリウムカルシウムのＨＡＡＤＦ－ＳＴＥＭ観察写真である。1 is a HAADF-STEM observation photograph of the barium calcium titanate obtained in Example 1. 実施例１で得られたチタン酸バリウムカルシウムのＨＡＡＤＦ－ＳＴＥＭ観察写真である（Ｂａ：白、Ｔｉ：灰色）。1 is a HAADF-STEM observation photograph of the barium calcium titanate obtained in Example 1 (Ba: white, Ti: gray). 実施例１で得られたチタン酸バリウムカルシウムについて、図４と同じ視野で実施したＥＤＳマッピングである（Ｂａ：白のみ表示）。FIG. 5 is an EDS mapping of the barium calcium titanate obtained in Example 1, performed in the same field of view as in FIG. 4 (Ba: only white is displayed). 実施例１で得られたチタン酸バリウムカルシウムについて、図４と同じ視野で実施したＥＤＳマッピングである（Ｃａ：白のみ表示）。FIG. 5 is an EDS mapping of the barium calcium titanate obtained in Example 1, performed in the same field of view as in FIG. 4 (Ca: only white is shown). 実施例７で得られたチタン酸バリウムカルシウムのＸＲＤ測定結果である。1 shows the results of XRD measurement of barium calcium titanate obtained in Example 7.
以下、本発明の好ましい形態について具体的に説明するが、本発明は以下の記載のみに限定されるものではなく、本発明の要旨を変更しない範囲において適宜変更して適用することができる。 The following provides a detailed description of a preferred embodiment of the present invention, but the present invention is not limited to the following description, and can be modified as appropriate without departing from the spirit of the present invention.
１．ペロブスカイト型化合物
本発明のペロブスカイト型化合物は、下記一般式（１）：
Ｂａ（１－ｘ）ＡｘＴｉＯ３　　　（１）
（式中、ＡはＣａ又はＳｒを表す。ｘは、０．００＜ｘ≦０．３０の数である。）で表され、走査電子顕微鏡観察から得られる平均粒子径（円相当径）に対する粒子径の標準偏差の割合（粒子径の標準偏差／平均粒子径×１００）で表されるＣＶ値が２０％以下であることを特徴とする。このような粒子サイズの均一性の高いペロブスカイト型化合物を用いることで、均一な誘電特性を有する誘電体層を形成することができるため、セラミックコンデンサの誘電体層の材料として好適である。更に粒子サイズの均一性の高い本発明のペロブスカイト型化合物は溶媒や樹脂への分散性が高い特徴も有し、この点でも樹脂等と混合してセラミックコンデンサの誘電体層を形成する材料として好適である。
本発明のペロブスカイト型化合物のＣＶ値は２０％以下であればよいが、１９％以下であることが好ましい。より好ましくは、１８．５％以下であり、更に好ましくは、１８％以下、特に好ましくは、１７．５％以下、中でも特に好ましくは、１７％以下であり、最も好ましくは、１６％以下である。
ペロブスカイト型化合物のＣＶ値は後述する実施例に記載の方法で測定することができる。 1. Perovskite Compound The perovskite compound of the present invention is represented by the following general formula (1):
Ba (1-x) A x TiO 3 (1)
(wherein A represents Ca or Sr, and x is a number satisfying 0.00<x≦0.30), and is characterized in that the CV value, which is expressed as the ratio of the standard deviation of the particle diameter to the average particle diameter (circle-equivalent diameter) obtained by observation with a scanning electron microscope (standard deviation of particle diameter/average particle diameter×100), is 20% or less. By using such a perovskite type compound having a high uniformity of particle size, a dielectric layer having uniform dielectric properties can be formed, and therefore the compound is suitable as a material for the dielectric layer of a ceramic capacitor. Furthermore, the perovskite type compound of the present invention having a high uniformity of particle size is also characterized by high dispersibility in solvents and resins, and in this respect, the compound is also suitable as a material for forming the dielectric layer of a ceramic capacitor by mixing with a resin or the like.
The CV value of the perovskite compound of the present invention may be 20% or less, and is preferably 19% or less, more preferably 18.5% or less, even more preferably 18% or less, particularly preferably 17.5% or less, particularly preferably 17% or less, and most preferably 16% or less.
The CV value of the perovskite compound can be measured by the method described in the Examples below.
本発明のペロブスカイト型化合物は、ＢＥＴ比表面積が５～７０ｍ２／ｇであることが好ましい。このようなＢＥＴ比表面積を有する、粒径の小さい粒子であると、積層セラミックスコンデンサ等の電子材料用途により適したものとなる。また、分散工程において再凝集成分を少なくし、易分散化する上では、ＢＥＴ比表面積が小さいものの方が好適である。ペロブスカイト型化合物のＢＥＴ比表面積は、より好ましくは、８～３５ｍ２／ｇであり、更に好ましくは、１０～３０ｍ２／ｇであり、最も好ましくは、１５～２５ｍ２／ｇである。
ペロブスカイト型化合物のＢＥＴ比表面積は後述する実施例に記載の方法で測定することができる。 The perovskite compound of the present invention preferably has a BET specific surface area of 5 to 70 m 2 /g. Small particles having such a BET specific surface area are more suitable for electronic material applications such as multilayer ceramic capacitors. Furthermore, in order to reduce re-aggregated components in the dispersion step and facilitate dispersion, a small BET specific surface area is preferable. The BET specific surface area of the perovskite compound is more preferably 8 to 35 m 2 /g, even more preferably 10 to 30 m 2 /g, and most preferably 15 to 25 m 2 /g.
The BET specific surface area of the perovskite compound can be measured by the method described in the Examples below.
本発明のペロブスカイト型化合物は、平均粒子径が１０～２１０ｎｍであることが好ましい。このような平均粒子径であると、誘電体層を形成する時に分散が容易で扱いやすく、均一な誘電体層を形成できる。平均粒子径は、より好ましくは、２０～１６０ｎｍであり、更に好ましくは、３０～１５０ｎｍであり、特に好ましくは、３５～１３０ｎｍであり、中でも特に好ましくは、４０～１００ｎｍであり、最も好ましくは、４５～６０ｎｍである。
ペロブスカイト型化合物の平均粒子径は、後述する実施例に記載の方法で測定することができる。 The perovskite compound of the present invention preferably has an average particle size of 10 to 210 nm. With such an average particle size, dispersion and handling are easy when forming a dielectric layer, and a uniform dielectric layer can be formed. The average particle size is more preferably 20 to 160 nm, even more preferably 30 to 150 nm, particularly preferably 35 to 130 nm, particularly preferably 40 to 100 nm, and most preferably 45 to 60 nm.
The average particle size of the perovskite compound can be measured by the method described in the Examples below.
本発明のペロブスカイト型化合物は、粒子の円形度が０．８５以上であることが好ましい。このような円形度であると、平滑な誘電体層を作製することが容易である。円形度は、より好ましくは、０．９０以上であり、更に好ましくは、０．９５以上である。
ペロブスカイト型化合物の粒子の円形度は、後述する実施例に記載の方法で測定することができる。 The perovskite compound of the present invention preferably has a particle circularity of 0.85 or more. With such a circularity, it is easy to prepare a smooth dielectric layer. The circularity is more preferably 0.90 or more, and even more preferably 0.95 or more.
The circularity of the perovskite compound particles can be measured by the method described in the Examples below.
本発明を用いて製造された粒子を用いてグリーンシートを想定した膜を作製し、その膜の表面平滑性を評価した場合、その表面の算術平均粗さ：Ｒａは、０．１１０μｍ以下であることが好ましい。より好ましくは、０．０９５μｍ以下であり、更に好ましくは、０．０８０μｍ以下であり、特に好ましくは、０．０７０μｍ以下である。
また、最大高さ：Ｒｚは、１．４００μｍ以下あることが好ましい。より好ましくは、１．２００μｍ以下であり、更に好ましくは、０．０８５μｍ以下であり、特に好ましくは、０．０８０μｍ以下である。
このような算術平均粗さ、最大高さであると、平滑な表面を作製することが容易である。ペロブスカイト型化合物の粒子を用いたグリーンシートを想定した膜の作製方法、及び、作製した膜の算術平均粗さ、最大高さは、後述する実施例に記載のとおりである。
このように、本発明の粒子を用いたグリーンシートに相当する膜を作製すると、表面が非常に平滑なものとすることができる。 When a film simulating a green sheet is produced using the particles produced according to the present invention and the surface smoothness of the film is evaluated, the arithmetic mean roughness (Ra) of the surface is preferably 0.110 μm or less, more preferably 0.095 μm or less, even more preferably 0.080 μm or less, and particularly preferably 0.070 μm or less.
The maximum height Rz is preferably 1.400 μm or less, more preferably 1.200 μm or less, even more preferably 0.085 μm or less, and particularly preferably 0.080 μm or less.
With such an arithmetic mean roughness and maximum height, it is easy to produce a smooth surface. The method for producing a film assuming a green sheet using particles of a perovskite compound, and the arithmetic mean roughness and maximum height of the produced film are as described in the examples below.
In this way, when a film equivalent to a green sheet is produced using the particles of the present invention, it is possible to obtain a very smooth surface.
上記一般式（１）で表されるペロブスカイト型化合物は、一般式（１）におけるｘが、０．００＜ｘ≦０．３０の数であり、カルシウムやストロンチウムの固溶量が少ない、ｘが０．００＜ｘ≦０．１５の数のものや、カルシウムやストロンチウムの固溶量が多い、ｘが０．１５＜ｘ≦０．３０の数のもののいずれも含まれるが、ｘは０．００５≦ｘ≦０．０５であることが好ましい。より好ましくは、０．０１≦ｘ≦０．０３である。
カルシウムやストロンチウムの固溶量が少ない、ｘが０．００＜ｘ≦０．１５の数のペロブスカイト型化合物は、積層セラミックコンデンサの中でも、強誘電性を高く維持しつつ温度特性や信頼性に優れるといった小型高容量化と信頼性良化のバランスが求められる民生向けコンデンサ（スマートフォンやタブレット等）に好適であると考えられる。また、カルシウムやストロンチウムの固溶量が多い、ｘが０．１５＜ｘ≦０．３０の数のペロブスカイト型化合物は、固溶量が増えることで更に温度特性が良化することが考えられ、より高温での耐熱性を求められる車載用コンデンサに好適であると考えられる。 The perovskite type compound represented by the above general formula (1) includes both those in which x in general formula (1) is a number in the range of 0.00<x≦0.30 and the amount of calcium or strontium dissolved in solid solution is small, where x is a number in the range of 0.00<x≦0.15, and those in which the amount of calcium or strontium dissolved in solid solution is large, where x is a number in the range of 0.15<x≦0.30, but it is preferable that x is 0.005≦x≦0.05, and more preferably 0.01≦x≦0.03.
Perovskite compounds with a small amount of calcium or strontium dissolved, where x is a number of 0.00<x≦0.15, are considered to be suitable for consumer capacitors (such as smartphones and tablets) that require a balance between small size, high capacity, and improved reliability, such as excellent temperature characteristics and reliability while maintaining high ferroelectricity, among other multilayer ceramic capacitors. Also, perovskite compounds with a large amount of calcium or strontium dissolved, where x is a number of 0.15<x≦0.30, are considered to be suitable for automotive capacitors that require heat resistance at higher temperatures, as the increased amount of solid solution further improves temperature characteristics.
２．ペロブスカイト型化合物の製造方法
本発明のペロブスカイト型化合物の製造方法は、バリウム化合物とチタン化合物水溶液とを混合してチタン酸バリウム分散液を得るチタン酸バリウム分散液調製工程と、チタン酸バリウム分散液調製工程で得られたチタン酸バリウム分散液を洗浄処理してチタン元素に対するバリウム元素のモル比が１．００未満であるチタン酸バリウムを得る脱バリウムイオン処理工程と、脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、熱処理する熱処理工程と、熱処理工程で得られた化合物を溶媒中で加熱して解粒する解粒工程とを含む製造方法を用いる。そして該製造方法において、チタン酸バリウム分散液調製工程で、バリウム化合物中のバリウム元素とチタン化合物水溶液中のチタン元素とのモル比（Ｂａ／Ｔｉ）が４．５以上となるようにバリウム化合物とチタン化合物水溶液とを用いる（以下、第一条件とも記載する）か、脱バリウムイオン処理工程に用いるチタン酸バリウム分散液中のチタン酸バリウム濃度を６５ｇ／Ｌ以上とする（以下、第二条件とも記載する）かの少なくとも一方を行うことを特徴とする。
チタン酸バリウム分散液調製工程は、目的とするチタン酸バリウムカルシウム又はチタン酸バリウムストロンチウムの前駆体となるチタン酸バリウム分散液を調製する工程である。チタン酸バリウム分散液調製工程で、第一条件を満たすようにバリウム化合物とチタン化合物水溶液とを用いると、系中に一定のバリウムイオンがある状態で前駆体であるチタン酸バリウム分散液が調製されることになり、これにより凝集の少ないチタン酸バリウムスラリーを得ることができる。そしてこのような凝集の少ないチタン酸バリウムスラリーを前駆体として脱バリウムイオン処理工程～解粒工程を行ってチタン酸バリウムカルシウム又はチタン酸バリウムストロンチウムを製造すると、粒子サイズの均一性が高いチタン酸バリウムカルシウム又はチタン酸バリウムストロンチウムを得ることができる。
また、第二条件を満たすようにすると、分散液中に一定以上のバリウムイオンが存在するようにして第二工程を行うことになり、そのようにすることでも同様に、粒子サイズの均一性が高いチタン酸バリウムカルシウム又はチタン酸バリウムストロンチウムを得ることができる。 2. Manufacturing Method of Perovskite Compound The manufacturing method of the perovskite compound of the present invention uses a manufacturing method including a barium titanate dispersion preparation step of mixing a barium compound with an aqueous titanium compound solution to obtain a barium titanate dispersion, a barium ion de-ionization treatment step of washing the barium titanate dispersion obtained in the barium titanate dispersion preparation step to obtain barium titanate having a molar ratio of barium element to titanium element of less than 1.00, a heat treatment step of mixing the barium titanate obtained in the barium ion de-ionization treatment step with a calcium salt or a strontium salt and subjecting the mixture to heat treatment, and a disintegration step of heating the compound obtained in the heat treatment step in a solvent to disintegrate the compound. The manufacturing method is characterized in that in the barium titanate dispersion preparation step, a barium compound and an aqueous titanium compound solution are used so that the molar ratio (Ba/Ti) of the barium element in the barium compound to the titanium element in the aqueous titanium compound solution is 4.5 or more (hereinafter also referred to as the first condition), or the barium titanate concentration in the barium titanate dispersion used in the barium ion debarium treatment step is 65 g/L or more (hereinafter also referred to as the second condition).
The barium titanate dispersion preparation step is a step of preparing a barium titanate dispersion that is a precursor of the desired barium calcium titanate or barium strontium titanate. In the barium titanate dispersion preparation step, if a barium compound and a titanium compound aqueous solution are used so as to satisfy the first condition, the precursor barium titanate dispersion is prepared in a state in which a certain amount of barium ions are present in the system, and this allows a barium titanate slurry with little aggregation to be obtained. Then, if barium calcium titanate or barium strontium titanate is produced by carrying out the barium ion removal process and the disintegration process using such a barium titanate slurry with little aggregation as a precursor, barium calcium titanate or barium strontium titanate with high uniformity in particle size can be obtained.
In addition, by satisfying the second condition, the second step is carried out in such a manner that a certain amount of barium ions are present in the dispersion liquid, and in this manner, barium calcium titanate or barium strontium titanate having a high degree of particle size uniformity can be obtained.
（１）チタン酸バリウム分散液調製工程
本発明のペロブスカイト型化合物の製造方法において、第一条件を満たすようにする場合、バリウム元素とチタン元素とのモル比（Ｂａ／Ｔｉ）は４．５以上であればよいが、５以上であることが好ましい。より好ましくは、６以上である。また、ペロブスカイト型化合物の製造コストを考慮すると、バリウム元素とチタン元素とのモル比（Ｂａ／Ｔｉ）は１０以下とすることが好ましい。 (1) Barium titanate dispersion preparation step In the method for producing a perovskite compound of the present invention, in order to satisfy the first condition, the molar ratio of barium element to titanium element (Ba/Ti) may be 4.5 or more, and is preferably 5 or more, and more preferably 6 or more. In addition, in consideration of the production cost of the perovskite compound, the molar ratio of barium element to titanium element (Ba/Ti) is preferably 10 or less.
本発明のペロブスカイト型化合物の製造方法を、第二条件を満たすようにして行う場合、上記チタン酸バリウム分散液調製工程においては、チタン化合物水溶液中のチタン元素のモル数に対するバリウム化合物中のバリウム元素のモル数は５未満であってもよいが、チタン酸バリウムの調製の効率を考慮すると、０．５以上となるようにチタン化合物水溶液とバリウム化合物とを用いることが好ましい。 When the method for producing a perovskite compound of the present invention is carried out so as to satisfy the second condition, in the barium titanate dispersion preparation step, the number of moles of barium element in the barium compound relative to the number of moles of titanium element in the titanium compound aqueous solution may be less than 5, but considering the efficiency of preparation of barium titanate, it is preferable to use the titanium compound aqueous solution and the barium compound so that the ratio is 0.5 or more.
上記チタン酸バリウム分散液調製工程に用いるバリウム化合物としては、特に制限されないが、水酸化バリウム、蓚酸バリウム、酢酸バリウム、硝酸バリウム、亜硝酸バリウム、塩化バリウム、塩素酸バリウム、過塩素酸バリウム、臭化バリウム、臭素酸バリウム、ヨウ化バリウム、りん酸水素バリウム、窒化バリウム、酸化バリウム、過酸化バリウム、硫化バリウム、アジ化バリウム、フッ化バリウム、ギ酸バリウム、乳酸バリウム、メタりん酸バリウム、メタクリル酸バリウム、ロジゾン酸バリウム、酒石酸バリウム、硫酸バリウム、亜硫酸バリウム、トリフルオロメタンスルホン酸バリウム、ビス（アセチルアセトナト）ジアクアバリウム（ＩＩ）、安息香酸バリウム、２－エチルヘキサン酸バリウム、オクタン酸バリウム、オレイン酸バリウム、クエン酸バリウム、水素化バリウム、チオシアン酸バリウム、メタチタン酸バリウム、アルミン酸バリウム、クロム酸バリウム、鉄酸バリウム、ナフテン酸バリウム、プロピオン酸バリウム、ジプロピオン酸バリウム、六ほう酸バリウム、ラウリン酸バリウム、マロン酸バリウム、チオ硫酸バリウム、トリフルオロ酢酸バリウム、トリメチル酢酸バリウム、リンゴ酸バリウム、コハク酸バリウム、吉草酸バリウム、カンファー酸バリウム、ピクリン酸バリウム、カプロン酸バリウム、グルコン酸バリウム、ベンゼンスルホン酸バリウム、サリチル酸バリウム、マンデル酸バリウム、ケイ皮酸バリウム、ステアリン酸バリウム、パルミチン酸バリウム、ミリスチン酸バリウム、ラウリン酸バリウム、スルファミン酸バリウム等が挙げられ、これらの１種又は２種以上を用いることができる。
これらの中でも、水酸化バリウム、酸化バリウム等の水溶液が塩基性となる化合物が好ましい。より好ましくは、水酸化バリウムである。 The barium compound used in the barium titanate dispersion preparation step is not particularly limited, but may be barium hydroxide, barium oxalate, barium acetate, barium nitrate, barium nitrite, barium chloride, barium chlorate, barium perchlorate, barium bromide, barium bromate, barium iodide, barium hydrogen phosphate, barium nitride, barium oxide, barium peroxide, barium sulfide, barium azide, barium fluoride, barium formate, barium lactate, barium metaphosphate, barium methacrylate, barium rhodizonate, barium tartrate, barium sulfate, barium sulfite, barium trifluoromethanesulfonate, bis(acetylacetonato)diaquabarium(II), barium benzoate, barium 2-ethylhexanoate, barium octanoate, barium oleate, barium citrate, Examples of suitable barium salts include barium hydride, barium thiocyanate, barium metatitanate, barium aluminate, barium chromate, barium ferrate, barium naphthenate, barium propionate, barium dipropionate, barium hexaborate, barium laurate, barium malonate, barium thiosulfate, barium trifluoroacetate, barium trimethylacetate, barium malate, barium succinate, barium valerate, barium camphorate, barium picrate, barium caproate, barium gluconate, barium benzenesulfonate, barium salicylate, barium mandelate, barium cinnamate, barium stearate, barium palmitate, barium myristate, barium laurate, and barium sulfamate. These may be used alone or in combination.
Among these, compounds that make aqueous solutions of barium hydroxide and barium oxide basic are preferred, and barium hydroxide is more preferred.
上記チタン酸バリウム分散液調製工程に用いるチタン化合物水溶液としては、四塩化チタン、水溶性チタン錯体等の水溶液が挙げられ、これらの１種又は２種以上を用いることができる。水溶性チタン錯体の配位子は、ヒドロキシ酸（塩）を含むことが好ましい。ヒドロキシ酸としては、α－ヒドロキシ酸であってもよい。α－ヒドロキシ酸は、例えば、グリコール酸、クエン酸、リンゴ酸、酒石酸、乳酸等を含む。また、配位子として乳酸のアンモニウム塩を含むチタン錯体であってもよい。例えば、チタニウムビス（アンモニウムラクテート）ジヒドロキシド（ＴＡＬＨ）が挙げられる。
これらの中でも、四塩化チタンの水溶液、ＴＡＬＨの水溶液が好ましい。より好ましくは、四塩化チタンの水溶液である。 The titanium compound aqueous solution used in the barium titanate dispersion preparation step includes an aqueous solution of titanium tetrachloride, a water-soluble titanium complex, etc., and one or more of these can be used. The ligand of the water-soluble titanium complex preferably contains a hydroxy acid (salt). The hydroxy acid may be an α-hydroxy acid. The α-hydroxy acid includes, for example, glycolic acid, citric acid, malic acid, tartaric acid, lactic acid, etc. Also, the titanium complex may contain an ammonium salt of lactic acid as a ligand. For example, titanium bis(ammonium lactate) dihydroxide (TALH) can be mentioned.
Among these, an aqueous solution of titanium tetrachloride and an aqueous solution of TALH are preferred, and an aqueous solution of titanium tetrachloride is more preferred.
上記チタン酸バリウム分散液調製工程においてチタン化合物水溶液と混合する際、バリウム化合物は固体のままで混合してもよいが、十分な量のチタン酸バリウムを生成させるため、溶液にしたうえで混合することが好ましい。
バリウム化合物溶液を調製するために用いる溶媒としては、有機溶媒、無機溶媒のいずれであってもよいが、水やメタノール、エタノールなどの水混和性有機溶媒が挙げられ、これらの１種又は２種以上を用いることができる。これらの中でも、水もしくは水混和性有機溶媒と水との混合物を用いることが好ましい。 When mixing with the aqueous titanium compound solution in the above-mentioned barium titanate dispersion preparation process, the barium compound may be mixed as a solid, but in order to produce a sufficient amount of barium titanate, it is preferable to mix it after making it into a solution.
The solvent used to prepare the barium compound solution may be either an organic solvent or an inorganic solvent, but may be water or a water-miscible organic solvent such as methanol or ethanol, and one or more of these may be used. Among these, it is preferable to use water or a mixture of a water-miscible organic solvent and water.
上記チタン酸バリウム分散液調製工程において、バリウム化合物とチタン化合物水溶液とを混合する際、これらを一括で添加して混合してもよく、分割添加してもよく、逐次添加してもよい。また、容器にバリウム化合物とチタン化合物水溶液の両方を添加してもよく、一方に他方を添加してもよい。 When mixing the barium compound and the aqueous titanium compound solution in the above-mentioned barium titanate dispersion preparation process, they may be added all at once, added in portions, or added successively. In addition, both the barium compound and the aqueous titanium compound solution may be added to a container, or one may be added to the other.
上記チタン酸バリウム分散液調製工程における溶媒の使用量は特に制限されないが、生成するチタン酸バリウム分散液における固形分濃度が１０～１０００ｇ／Ｌとなる量が好ましい。より好ましくは、１０～５００ｇ／Ｌであり、更に好ましくは、１０～２５０ｇ／Ｌであり、最も好ましくは、１０～１００ｇ／Ｌである。固形分濃度が低すぎると、ペロブスカイト化合物の生産能力が低下し、固形分濃度が高すぎると脱バリウムイオン処理工程での洗浄処理が不均一化する虞がある。
ここでいう溶媒の使用量とは、チタン化合物水溶液に含まれる水と、バリウム化合物を溶液にして混合する場合のバリウム化合物溶液に含まれる溶媒との合計量である。 The amount of the solvent used in the barium titanate dispersion preparation step is not particularly limited, but is preferably an amount that results in a solids concentration in the resulting barium titanate dispersion of 10 to 1000 g/L, more preferably 10 to 500 g/L, even more preferably 10 to 250 g/L, and most preferably 10 to 100 g/L. If the solids concentration is too low, the productivity of the perovskite compound decreases, and if the solids concentration is too high, there is a risk of the washing treatment in the barium ion removal treatment step becoming non-uniform.
The amount of the solvent used here refers to the total amount of water contained in the aqueous titanium compound solution and the solvent contained in the barium compound solution when the barium compound is mixed in the form of a solution.
上記チタン酸バリウム分散液調製工程においては、バリウム化合物とチタン化合物水溶液との混合溶液のｐＨが５以上になるように調整することが好ましい。このようなアルカリ性の領域で混合することで、十分な量のチタン酸バリウムを生成させることができる。バリウム化合物とチタン化合物水溶液との混合溶液のｐＨは、より好ましくは、８以上であり、更に好ましくは、１０以上である。 In the above-mentioned barium titanate dispersion preparation process, it is preferable to adjust the pH of the mixed solution of the barium compound and the aqueous titanium compound solution to 5 or more. By mixing in such an alkaline range, a sufficient amount of barium titanate can be produced. The pH of the mixed solution of the barium compound and the aqueous titanium compound solution is more preferably 8 or more, and even more preferably 10 or more.
（２）脱バリウムイオン処理工程
本発明のペロブスカイト型化合物の製造方法において、第二条件を満たすようにする場合、チタン酸バリウム分散液中のチタン酸バリウム濃度は６５ｇ／Ｌ以上であればよいが、８０ｇ／Ｌ以上であることが好ましい。より好ましくは、１１０ｇ／Ｌ以上である。 (2) Barium ion removal process In the method for producing a perovskite compound of the present invention, in order to satisfy the second condition, the barium titanate concentration in the barium titanate dispersion may be 65 g/L or more, preferably 80 g/L or more, and more preferably 110 g/L or more.
本発明のペロブスカイト型化合物の製造方法を、第一条件を満たすようにして行う場合、脱バリウムイオン処理工程に用いるチタン酸バリウム分散液中のチタン酸バリウム濃度は６５ｇ／Ｌ未満であってもよいが、ペロブスカイト型化合物の製造の効率を考慮すると、１０ｇ／Ｌ以上とすることが好ましい。 When the method for producing a perovskite compound of the present invention is carried out so as to satisfy the first condition, the barium titanate concentration in the barium titanate dispersion liquid used in the barium ion removal treatment step may be less than 65 g/L, but considering the efficiency of producing the perovskite compound, it is preferable that it is 10 g/L or more.
上記脱バリウムイオン処理工程では、チタン酸バリウム分散液調製工程で得られたチタン酸バリウム分散液を洗浄処理してチタン元素に対するバリウム元素のモル比を１．００未満とすることができればよい。
チタン元素に対するバリウム元素のモル比は、蛍光Ｘ線分析（ＸＲＦ）により確認することができる。 In the barium ion removing treatment step, it is only necessary to subject the barium titanate dispersion obtained in the barium titanate dispersion preparation step to a washing treatment so that the molar ratio of barium element to titanium element is less than 1.00.
The molar ratio of barium element to titanium element can be confirmed by X-ray fluorescence analysis (XRF).
上記脱バリウムイオン処理工程において行うチタン酸バリウムに対する洗浄処理によって、チタン酸バリウムから効率的にバリウムイオンを溶出させることができる。洗浄処理は、チタン元素に対するバリウム元素のモル比を１．００未満とすることができる処理であればよいが、チタン酸バリウムスラリーを撹拌しながら、酸を添加して行うことが好ましい。
脱バリウムイオン処理は、塩酸、硫酸、硝酸、リン酸等の無機酸や、酢酸、シュウ酸、クエン酸等の有機酸を用いた酸による洗浄処理によって行われることが好ましい。
なお、チタン元素に対するバリウム元素のモル比を１．００未満とする処理は水洗によって行っても良いが、膨大な量の水を必要とするため現実的ではなく、酸を用いてバリウムイオンを溶出させることが定量的であり、かつ工業的製造に適している。 The barium titanate is washed in the barium ion removing process to efficiently dissolve barium ions from the barium titanate. The washing process may be any process capable of making the molar ratio of barium element to titanium element less than 1.00, and is preferably carried out by adding an acid while stirring the barium titanate slurry.
The barium ion removal treatment is preferably carried out by a washing treatment using an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, or an organic acid such as acetic acid, oxalic acid, or citric acid.
The treatment to make the molar ratio of barium element to titanium element less than 1.00 can be carried out by washing with water, but this is not practical because it requires a huge amount of water. Instead, it is quantitative to elute barium ions using an acid, and this is suitable for industrial production.
上記脱バリウムイオン処理工程における脱バリウムイオン処理の方法はチタン酸バリウムのチタン元素に対するバリウム元素のモル比を１．００未満とすることができる限り特に制限されないが、チタン酸バリウムに酸を添加し、得られたスラリーのｐＨが５～１１となるようにして行うことが好ましい。また、スラリーのｐＨは、脱バリウムイオン処理工程で脱バリウムイオン処理をするチタン酸バリウムの比表面積やバリウム元素をカルシウム元素又はストロンチウム元素に置換する量に応じて上記ｐＨの範囲内で適宜調整して行うことが好ましい。例えば、ＢＥＴ比表面積が７５～１２０ｍ２／ｇのチタン酸バリウムをｐＨ＝７で脱バリウムイオン処理した場合は、バリウム元素のモル比は約０．６０～０．７０となり、ｐＨ＝１１で処理した場合は約０．７５～０．９０となる。 The method of debarium ion treatment in the above-mentioned debarium ion treatment step is not particularly limited as long as the molar ratio of barium element to titanium element of barium titanate can be less than 1.00, but it is preferable to add an acid to barium titanate and perform the treatment so that the pH of the obtained slurry is 5 to 11. It is also preferable to appropriately adjust the pH of the slurry within the above-mentioned pH range depending on the specific surface area of the barium titanate to be debarium ion treated in the debarium ion treatment step and the amount of barium element substituted with calcium element or strontium element. For example, when barium titanate having a BET specific surface area of 75 to 120 m 2 /g is debarium ion treated at pH=7, the molar ratio of barium element is about 0.60 to 0.70, and when treated at pH=11, the molar ratio is about 0.75 to 0.90.
上記脱バリウムイオン処理工程の脱バリウムイオン処理を行った後のチタン酸バリウムを熱処理工程に供する前に水洗する工程を行うことが好ましい。これにより、チタン酸バリウムから酸及び溶出したバリウム元素を除くことができ、カルシウムやストロンチウムの固溶量が多く、かつ、不純物の少ないペロブスカイト型化合物を製造することができる。 It is preferable to carry out a water washing step before subjecting the barium titanate after the barium ion removal treatment in the barium ion removal treatment step to the heat treatment step. This makes it possible to remove the acid and the dissolved barium element from the barium titanate, and to produce a perovskite type compound with a large amount of calcium and strontium dissolved therein and with few impurities.
上記脱バリウムイオン処理工程の洗浄処理に関しては、バリウム元素を十分に溶出させることと製造の効率とを考えると、洗浄水の電気伝導度が１００μＳ／ｃｍ以下となるまで洗浄することが好ましい。より好ましくは、５０μＳ／ｃｍ以下である。 Regarding the washing process in the barium ion removal process, in consideration of sufficient elution of barium elements and production efficiency, washing is preferably performed until the electrical conductivity of the washing water is 100 μS/cm or less. More preferably, it is 50 μS/cm or less.
（３）熱処理工程
上記熱処理工程は、脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、熱処理する工程である。
チタン酸バリウムと混合するカルシウム塩、ストロンチウム塩は特に制限されず、カルシウムやストロンチウムの酸化物、水酸化物、塩化物、炭酸塩、硫酸塩、硝酸塩、リン酸塩、ヨウ化水素酸、酢酸塩、シュウ酸塩、クエン酸などの有機酸塩等が挙げられ、これらの１種又は２種以上を用いることができる。 (3) Heat Treatment Step The heat treatment step is a step in which the barium titanate obtained in the barium ion removal treatment step is mixed with a calcium salt or a strontium salt, and the mixture is subjected to a heat treatment.
The calcium salt and strontium salt to be mixed with barium titanate are not particularly limited, and examples thereof include calcium and strontium oxides, hydroxides, chlorides, carbonates, sulfates, nitrates, phosphates, and organic acid salts such as hydroiodic acid, acetates, oxalates, and citric acid, and one or more of these can be used.
上記熱処理工程でカルシウム塩を使用する場合、使用するカルシウム塩の量は、チタン酸バリウムが含むチタン元素１００モル％に対して、カルシウム塩に含まれるカルシウム元素の量が０モル％より多く、３０モル％以下となる量であることが好ましい。このような割合で用いることで、チタン酸バリウムにカルシウムが固溶し、かつ、チタン酸バリウムカルシウム以外の結晶相を含まない純度の高いものが合成できる。使用するカルシウム塩の量は、より好ましくは、チタン酸バリウムが含むチタン元素１００モル％に対して、カルシウム塩に含まれるカルシウム元素の量が０．５～２０モル％となる量であり、更に好ましくは、カルシウム元素の量が１～１０モル％となる量である。
上記熱処理工程でストロンチウム塩を使用する場合も、チタン酸バリウムが含むチタン元素１００モル％に対して、ストロンチウム塩に含まれるストロンチウム元素の量が上記と同様の割合となるように使用することが好ましい。 When a calcium salt is used in the heat treatment step, the amount of calcium salt used is preferably such that the amount of calcium element contained in the calcium salt is more than 0 mol% and 30 mol% or less relative to 100 mol% of titanium element contained in barium titanate. By using the calcium salt in such a ratio, calcium is dissolved in barium titanate and a high purity product that does not contain any crystal phase other than barium calcium titanate can be synthesized. The amount of calcium salt used is more preferably such that the amount of calcium element contained in the calcium salt is 0.5 to 20 mol% relative to 100 mol% of titanium element contained in barium titanate, and even more preferably such that the amount of calcium element is 1 to 10 mol%.
When a strontium salt is used in the heat treatment step, it is also preferable to use the strontium salt so that the amount of elemental strontium contained in the strontium salt is in the same ratio as above relative to 100 mol % of elemental titanium contained in barium titanate.
また熱処理工程においては、カルシウム塩又はストロンチウム塩に加えて、更にバリウム塩をチタン酸バリウムと混合してもよい。バリウム塩を混合することで熱処理によるペロブスカイト型化合物の挙動をコントロールすることができ、粒子径を制御できる。
バリウム塩の使用量は所望の粒子径等に応じて適宜設定することができる。 In the heat treatment step, in addition to the calcium salt or strontium salt, a barium salt may be further mixed with the barium titanate. By mixing the barium salt, the behavior of the perovskite compound during the heat treatment can be controlled, and the particle size can be controlled.
The amount of the barium salt used can be appropriately determined depending on the desired particle size, etc.
上記熱処理工程において、チタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合する方法は、これらが十分に混合される限り特に制限されないが、例えば、チタン酸バリウムスラリー中にカルシウム塩又はストロンチウム塩を添加した後、撹拌機等でスラリーを撹拌することが挙げられる。バリウム塩を混合する方法も同様である。 In the above heat treatment step, the method for mixing barium titanate with a calcium salt or a strontium salt is not particularly limited as long as they are thoroughly mixed, but an example of this is adding a calcium salt or a strontium salt to a barium titanate slurry and then stirring the slurry with a stirrer or the like. The same method is used for mixing the barium salt.
上記熱処理工程において、チタン酸バリウムとカルシウム塩又はストロンチウム塩との混合物を熱処理する際の温度は、４００～１２００℃であることが好ましい。より好ましくは、４５０～１０００℃であり、更に好ましくは、５００～８００℃、特に好ましくは、５５０～７００℃である。
また熱処理する時間は、０．５～１２時間であることが好ましい。より好ましくは、１～１０時間であり、更に好ましくは、２～８時間である。
熱処理する雰囲気は特に制限されず、空気下であってもよく、窒素、アルゴン等の不活性ガス雰囲気下であってもよい。 In the heat treatment step, the temperature for heat treating the mixture of barium titanate and a calcium salt or a strontium salt is preferably 400 to 1200° C., more preferably 450 to 1000° C., even more preferably 500 to 800° C., and particularly preferably 550 to 700° C.
The heat treatment time is preferably 0.5 to 12 hours, more preferably 1 to 10 hours, and even more preferably 2 to 8 hours.
The atmosphere in which the heat treatment is carried out is not particularly limited, and may be air or an inert gas atmosphere such as nitrogen or argon.
上記熱処理工程において熱処理を行う回数は特に制限されず、１回であってもよく、複数回行ってもよい。好ましくは、脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、加熱乾燥して乾燥混合物を得た後、乾燥混合物を焼成することである。
チタン酸バリウムとカルシウム塩又はストロンチウム塩との混合物を焼成する前に乾燥させることにより組成の偏析を抑え、カルシウム元素やストロンチウム元素が均一に分布した前駆体を得ることができる。そしてこのような前駆体を焼成することで、ペロブスカイト型化合物にカルシウム元素やストロンチウム元素が均一に固溶され、かつ粒子の均一性が向上する。
混合物を乾燥させる方法は特に制限されないが、箱型乾燥機、流動層乾燥機、気流式乾燥機、噴霧乾燥機のいずれかを用いる方法が好ましい。
以下においては、熱処理工程のうち、脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、加熱乾燥して乾燥混合物を得る工程を乾燥工程、乾燥混合物を焼成する工程を焼成工程ともいう。 The number of times of heat treatment in the heat treatment step is not particularly limited, and may be one or more times. Preferably, the barium titanate obtained in the barium ion removing treatment step is mixed with a calcium salt or a strontium salt, heated and dried to obtain a dry mixture, and then the dry mixture is fired.
By drying a mixture of barium titanate and a calcium salt or a strontium salt before firing, it is possible to suppress segregation of the composition and obtain a precursor in which calcium and strontium elements are uniformly distributed. By firing such a precursor, calcium and strontium elements are uniformly dissolved in the perovskite compound, and the uniformity of the particles is improved.
The method for drying the mixture is not particularly limited, but a method using any one of a tray dryer, a fluidized bed dryer, an airflow dryer, and a spray dryer is preferred.
In the following, the process of mixing the barium titanate obtained in the barium ion removal treatment process with a calcium salt or a strontium salt and heating and drying to obtain a dry mixture is also referred to as the drying process, and the process of firing the dry mixture is also referred to as the firing process.
上記熱処理工程において、乾燥工程と、乾燥混合物を焼成する焼成工程を行う場合、乾燥混合物を焼成する温度、時間は、上記熱処理工程の温度、時間と同様であることが好ましい。
上記乾燥工程での混合物の乾燥は、８０～３００℃で行うことが好ましい。より好ましくは、９０～１１０℃である。
また混合物を乾燥する時間は、箱型乾燥機であれば、０．５～２４時間であることが好ましい。より好ましくは、２～６時間である。 When the heat treatment step includes a drying step and a firing step of firing the dried mixture, the temperature and time for firing the dried mixture are preferably the same as those for the heat treatment step.
The mixture is preferably dried at 80 to 300° C. in the drying step, and more preferably at 90 to 110° C.
The time for drying the mixture is preferably 0.5 to 24 hours, more preferably 2 to 6 hours, in the case of a tray dryer.
（４）解粒工程
本発明のペロブスカイト型化合物の製造方法は更に、熱処理工程で得られたペロブスカイト型化合物を溶媒中で加熱して解粒する解粒工程を含む。これにより、粒子同士の連結が少ないペロブスカイト型化合物を得ることができる。
解粒工程においてペロブスカイト型化合物を溶媒中で加熱して解粒する際の加熱温度は、ペロブスカイト型化合物の粒子が解粒されることになる限り特に制限されないが、３０～５００℃であることが好ましい。ペロブスカイト型化合物を溶媒中でこのような温度に加熱することで、ペロブスカイト型化合物の凝集粒子を十分に解粒し、粒子同士の連結が少なく、かつ、真球状に近い粒子の割合が多いペロブスカイト型化合物とすることができる。ペロブスカイト型化合物を加熱する温度は、３０～５００℃であることが好ましいが、ペロブスカイト型化合物の凝集粒子をより十分に解粒する点から、６０～３００℃であることがより好ましい。更に好ましくは、１００～２００℃であり、特に好ましくは、１００～１８０℃である。 (4) Disintegration step The method for producing a perovskite compound of the present invention further includes a disintegration step of heating the perovskite compound obtained in the heat treatment step in a solvent to disintegrate the particles, thereby obtaining a perovskite compound with few connections between particles.
The heating temperature when the perovskite compound is heated in a solvent to disintegrate in the disintegration step is not particularly limited as long as the particles of the perovskite compound are disintegrated, but is preferably 30 to 500 ° C. By heating the perovskite compound in a solvent to such a temperature, the aggregated particles of the perovskite compound can be sufficiently disintegrated, and a perovskite compound having few connections between particles and a high proportion of particles that are close to spherical can be obtained. The temperature at which the perovskite compound is heated is preferably 30 to 500 ° C., but is more preferably 60 to 300 ° C. from the viewpoint of more sufficiently disintegrating the aggregated particles of the perovskite compound. More preferably, it is 100 to 200 ° C., and particularly preferably, it is 100 to 180 ° C.
上記解粒工程においてペロブスカイト型化合物を加熱する時間は特に制限されないが、ペロブスカイト型化合物の凝集粒子を十分に解粒する点から、１～１２０時間であることが好ましい。より好ましくは、２～７２時間であり、更に好ましくは、４～６０時間であり、特に好ましくは、１０～４０時間である。また、求められる特性によっては製造の効率を考慮して１０～３０時間としてもよい。
また、加熱する雰囲気は特に制限されず、空気下であってもよく、窒素、アルゴン等の不活性ガス雰囲気下であってもよい。 The time for heating the perovskite compound in the disintegration step is not particularly limited, but is preferably 1 to 120 hours from the viewpoint of sufficiently disintegrating aggregated particles of the perovskite compound. More preferably, it is 2 to 72 hours, even more preferably, it is 4 to 60 hours, and particularly preferably, it is 10 to 40 hours. Depending on the desired properties, it may be 10 to 30 hours in consideration of production efficiency.
The atmosphere in which the heating is performed is not particularly limited, and may be air or an inert gas atmosphere such as nitrogen or argon.
上記解粒工程においてペロブスカイト型化合物を加熱する際に使用する溶媒としては、有機溶媒、無機溶媒のいずれであってもよいが、水やメタノール、エタノールなどの水混和性有機溶媒が挙げられ、これらの１種又は２種以上を用いることができる。これらの中でも、水もしくは水混和性有機溶媒と水との混合物を用いることが好ましい。 The solvent used when heating the perovskite compound in the above-mentioned disintegration step may be either an organic solvent or an inorganic solvent, but examples of the solvent include water and water-miscible organic solvents such as methanol and ethanol, and one or more of these can be used. Among these, it is preferable to use water or a mixture of a water-miscible organic solvent and water.
上記解粒工程は、溶媒中に酸や塩基、又は、溶媒中で酸や塩基としてはたらくものを添加して行ってもよい。これらを溶媒中に添加することで、より効率的に凝集粒子を解粒することができる。
酸としては、上記脱バリウムイオン処理工程で脱バリウムイオン処理をする場合に用いるものと同様の酸が挙げられる。
塩基としては、水酸化リチウム、水酸化ナトリウム、水酸化カリウム、水酸化バリウムのようなアルカリ金属やアルカリ土類金属の水酸化物等の無機塩基や、有機アミン類等の有機塩基が挙げられる。中でも、ペロブスカイト型化合物の凝集粒子の解粒効果が高いことから、水酸化バリウムを用いることが好ましい。
酸や塩基、又は、溶媒中で酸や塩基としてはたらくものは、それぞれ１種を用いてもよく、２種以上を用いてもよい。 The disintegration step may be carried out by adding an acid or a base, or a substance that acts as an acid or a base in the solvent, to the solvent. By adding these to the solvent, the aggregated particles can be disintegrated more efficiently.
The acid may be the same as that used in the barium ion removal treatment in the barium ion removal treatment step.
Examples of the base include inorganic bases such as hydroxides of alkali metals or alkaline earth metals, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and barium hydroxide, and organic bases such as organic amines. Among these, it is preferable to use barium hydroxide because of its high effect of deagglomerating aggregated particles of the perovskite compound.
The acids and bases, or those which act as acids and bases in a solvent, may each be used alone or in combination of two or more.
（５）その他の工程
本発明のペロブスカイト型化合物の製造方法は、上述した工程以外のその他の工程を含んでいてもよい。その他の工程としては、熱処理工程又は解粒工程で得られたペロブスカイト型化合物を分散する工程や洗浄する工程、洗浄後のペロブスカイト型化合物を乾燥する工程が挙げられる。
ペロブスカイト型化合物を分散する工程における分散方法は特に制限されないが、ビーズミルのようなメディアを使用した分散機や乳化機や超音波式分散機などのメディアレス分散機を使用する方法が挙げられる。
ペロブスカイト型化合物を洗浄する工程における洗浄方法は特に制限されないが、水洗が好ましい。
洗浄後のペロブスカイト型化合物を乾燥する工程における乾燥方法は特に制限されないが、箱型乾燥機、流動層乾燥機、気流式乾燥機、噴霧乾燥機のいずれかを使用し、例えば、箱型乾燥機であれば、８０～３００℃の雰囲気下に０．５～２４時間静置する方法等が挙げられる。 (5) Other Steps The method for producing a perovskite compound of the present invention may include other steps in addition to the steps described above. Examples of the other steps include a step of dispersing or washing the perovskite compound obtained in the heat treatment step or the disintegration step, and a step of drying the washed perovskite compound.
The dispersion method in the step of dispersing the perovskite compound is not particularly limited, but examples thereof include a method using a disperser using media such as a bead mill, or a media-less disperser such as an emulsifier or an ultrasonic disperser.
The washing method in the step of washing the perovskite compound is not particularly limited, but washing with water is preferred.
The drying method in the step of drying the washed perovskite compound is not particularly limited, and any one of a box dryer, a fluidized bed dryer, an air flow dryer, and a spray dryer may be used. For example, in the case of a box dryer, a method in which the compound is allowed to stand in an atmosphere at 80 to 300° C. for 0.5 to 24 hours may be mentioned.
本発明のペロブスカイト型化合物の製造方法は、粒子サイズの均一性の高いチタン酸バリウムカルシウムを製造することができる方法であり、そのような本発明の製造方法で得られる、本発明のペロブスカイト型化合物の１種であるチタン酸バリウムカルシウムは、積層セラミックコンデンサ等の電子材料用途に好適に用いることができる。 The method for producing the perovskite compound of the present invention is a method capable of producing barium calcium titanate having a high degree of uniformity in particle size, and the barium calcium titanate, which is one type of perovskite compound of the present invention and is obtained by the method for producing the perovskite compound of the present invention, can be suitably used for electronic material applications such as multilayer ceramic capacitors.
本発明を詳細に説明するために以下に具体例を挙げるが、本発明はこれらの例のみに限定されるものではない。特に断りのない限り、「％」及び「ｗｔ％」とは「重量％（質量％）」を意味する。なお、各物性の測定方法は以下の通りである。 Specific examples are given below to explain the present invention in detail, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "wt%" mean "weight % (mass %)". The methods for measuring each physical property are as follows.
＜組成分析＞
蛍光Ｘ線分析装置（（株）リガク製ＺＳＸ　ＰｒｉｍｕｓＩＩ、検量線法）を用いて、その組成分析を行うことで、Ｂａ／Ｔｉ、Ｃａ／Ｔｉ、（Ｂａ＋Ｃａ）／Ｔｉのモル比を求めた。
＜比表面積＞
チタン酸バリウム粉末とチタン酸バリウムカルシウム粉末の比表面積は、全自動比表面積測定装置（（株）マウンテック製Ｍａｃｓｏｒｂ　ＨＭ　ｍｏｄｅｌ－１２２０）を用いて、３５０℃で１５分脱気した後、ＢＥＴ１点法で測定した。
＜ＣＶ値・円形度の算出＞
走査型電子顕微鏡（ＳＵ８０２０（（株）日立ハイテク製））で３万倍粒子の画像を取得し、その画像を９分割したデータを画像解析ソフトＤｅｅｐＣｌｅ（堺化学工業株式会社製）に読み込ませ、解析モデルＶｅｒ．３．１８を用いて、平均粒子径（円相当径）および標準偏差σ（円相当径）を計量し、標準偏差を平均粒子径で除し、その値を１００倍することでＣＶ値：変動係数（％）を算出した。
円形度は１に近いほど円に近いことを表す。これを４π×（面積）／（周囲長の２乗）で定義し、画像解析ソフトＤｅｅｐＣｌｅの解析モデルＶｅｒ．３．１８を用いて、粒子の面積、周囲長を計量し、算出した。
＜点分析・ＥＤＳマッピング＞
原子分解能分析電子顕微鏡(日本電子株式会社製、ＪＥＭ－ＡＲＭ２００Ｆ)を用いて、その点分析およびＥＤＳマッピングを行った。
＜結晶構造＞
粉末Ｘ線解析装置（Ｂｒｕｋｅｒ社製、Ｄ８　ＡＤＶＡＮＣＥ、線源：ＣｕＫα)を用いて、その結晶構造を確認した。
＜グリーンシートを想定した膜の形成および評価＞
（分散処理）
ポリプロピレン容器に、分散剤（日油株式会社製、ＳＰ－０２０１）を０．２ｇ入れ、更にチタン酸バリウムカルシウム粉末を４ｇ、エタノールを２０ｇ入れ、チタン酸バリウムカルシウムの混合物を得た。この混合物に更にジルコニアビーズ（直径３ｍｍ）２５ｇを入れ、遊星ボールミルで分散処理を行い、ジルコニアビーズの除去を行った。
（有機ビヒクルの調整）
ガラスビーカーにエチルセルロース（キシダ化学株式会社製）１．２ｇ、テルピネオール（日本テルペン化学株式会社製）４８．８ｇを加え、加熱溶解し、有機ビヒクルを得た。
（グリーンシートを想定した膜の形成）
分散処理後の混合物１．０ｇ、有機ビヒクル０．８ｇを混合し、少量をガラス板上に滴下した。そしてガラス板上の混合物を、ギャップが７５μｍのアプリケーターを用いて膜にした。この膜を、１２０℃で１０分間乾燥させ、グリーンシートを想定した膜を得た。この膜の表面の粗さ（算術平均粗さ：Ｒａ、最大高さ：Ｒｚ）を表面粗さ計で測定した。表面の粗さは、ＳＵＲＦＣＯＭ　１３０Ａ（東京精密株式会社製）を用いて測定した。 <Composition Analysis>
The composition was analyzed using an X-ray fluorescence analyzer (ZSX Primus II, manufactured by Rigaku Corporation, calibration curve method) to determine the molar ratios of Ba/Ti, Ca/Ti, and (Ba+Ca)/Ti.
<Specific surface area>
The specific surface areas of the barium titanate powder and barium calcium titanate powder were measured by a BET single point method using a fully automatic specific surface area measuring device (Macsorb HM model-1220 manufactured by Mountec Co., Ltd.) after degassing at 350° C. for 15 minutes.
<Calculation of CV value and circularity>
A 30,000-fold magnification image of the particles was obtained using a scanning electron microscope (SU8020 (manufactured by Hitachi High-Tech Corporation)), and the image was divided into nine parts, and the resulting data was read into image analysis software DeepCle (manufactured by Sakai Chemical Industry Co., Ltd.). Using analysis model Ver. 3.18, the average particle size (equivalent circle diameter) and standard deviation σ (equivalent circle diameter) were measured, and the standard deviation was divided by the average particle size. The value was multiplied by 100 to calculate the CV value: coefficient of variation (%).
The closer the circularity is to 1, the closer it is to a circle. This is defined as 4π × (area) / (square of perimeter), and the area and perimeter of the particle were measured and calculated using the analysis model Ver. 3.18 of the image analysis software DeepCle.
<Point analysis/EDS mapping>
The point analysis and EDS mapping were carried out using an atomic resolution analytical electron microscope (JEM-ARM200F, manufactured by JEOL Ltd.).
<Crystal structure>
The crystal structure was confirmed using a powder X-ray analyzer (D8 ADVANCE, manufactured by Bruker, radiation source: CuKα).
<Formation and evaluation of a film assuming a green sheet>
(Distributed Processing)
0.2 g of a dispersant (NOF Corporation, SP-0201) was placed in a polypropylene container, followed by 4 g of barium calcium titanate powder and 20 g of ethanol to obtain a barium calcium titanate mixture. 25 g of zirconia beads (diameter 3 mm) were added to this mixture, which was then dispersed in a planetary ball mill, after which the zirconia beads were removed.
(Preparation of Organic Vehicle)
1.2 g of ethyl cellulose (Kishida Chemical Co., Ltd.) and 48.8 g of terpineol (Nihon Terpene Kagaku Co., Ltd.) were added to a glass beaker and dissolved by heating to obtain an organic vehicle.
(Formation of a film assuming a green sheet)
1.0 g of the mixture after dispersion treatment and 0.8 g of organic vehicle were mixed, and a small amount was dropped onto a glass plate. The mixture on the glass plate was then made into a film using an applicator with a gap of 75 μm. This film was dried at 120° C. for 10 minutes to obtain a film that was assumed to be a green sheet. The surface roughness of this film (arithmetic mean roughness: Ra, maximum height: Rz) was measured with a surface roughness meter. The surface roughness was measured using a SURFCOM 130A (manufactured by Tokyo Seimitsu Co., Ltd.).
実施例１
（チタン酸バリウム分散液調製工程）
５Ｌ容量の反応容器に純水１．３Ｌと水酸化バリウム八水和物（堺化学工業株式会社製）１１５７ｇを入れて加熱して水酸化バリウム八水和物を水に溶解させて、水酸化バリウム水溶液を調製した。
四塩化チタン溶液（富士フイルム和光純薬株式会社製、Ｔｉ換算で１８６ｇ／Ｌ濃度）０．２３Ｌを上記水酸化バリウム水溶液と混合し、ＢａＴｉＯ３換算で８０ｇ／Ｌ濃度のチタン酸バリウム前駆体水スラリーを得た。水酸化バリウム水溶液と四塩化チタン溶液の混合終了時点でのＢａ／Ｔｉモル比は４．０であった。
（脱バリウムイオン処理工程）
上記チタン酸バリウム前駆体スラリーを撹拌機で撹拌しながら、濃度２０％の硝酸水溶液を滴下し、スラリーのｐＨが１１．０になるように調整し、ｐＨを１時間維持させた。この後、濾過水洗し、濾液の電気電導度が５０μＳ／ｃｍ以下になるまで水洗を行い、水洗後のケーキを得た。このケーキに水を加え、液量を１Ｌにし、水洗後チタン酸バリウム原体スラリーを得た。上記で得られたスラリーから、一部サンプリングを行い、９５℃の箱型乾燥機で乾燥させた後、ＸＲＦ分析にてＢａ／Ｔｉモル比を求めたところ、０．８１４であった。このチタン酸バリウム前駆体水スラリーのＳＥＭ観察結果を図１－１に示す。図１－１では、得られたチタン酸バリウム前駆体に粒子の凝集はないことが確認された。
（熱処理工程（乾燥工程））
上記水洗後チタン酸バリウム原体スラリーに酢酸カルシウム１水和物（関東化学株式会社製）１２ｇ、水酸化バリウム八水和物（堺化学工業株式会社製）２７ｇを入れて撹拌機で撹拌した後、９５℃で噴霧乾燥させ、乳鉢等で解砕することで、チタン酸バリウムカルシウム前駆体粉末を得た。
（熱処理工程（焼成工程））
上記チタン酸バリウムカルシウム前駆体粉末２０ｇをアルミナ製ルツボに入れて、大気焼成炉にて６００℃で２時間熱処理させることでチタン酸バリウムカルシウム固着物を得た。
（解粒工程）
上記で得られたチタン酸バリウムカルシウム固着物１５ｇをオートクレーブ容器に入れ、純水７ｇと水酸化バリウム八水和物（堺化学工業株式会社製）１１ｇを加え、１６０℃で２４時間水熱処理した。オートクレーブ内容物を室温まで放冷し、回収したスラリーを濾過水洗し、濾液の電気伝導度が５０μＳ／ｃｍ以下になるまで洗浄を行った後、９５℃の箱型乾燥機で６時間乾燥させた。乾燥後の固着物を乳鉢で解砕することでチタン酸バリウムカルシウム粉末を得た。得られたチタン酸バリウムカルシウムのＳＥＭ観察結果を図１－２に、ＨＡＡＤＦ－ＳＴＥＭ像を図３、４に、ＥＤＳマッピングの結果を図５、６に示す。
図１－２では、得られたチタン酸バリウムカルシウムは球状であり、かつ粒子径が揃っていることが確認された。
図３のＨＡＡＤＦ－ＳＴＥＭ像中の０１の箇所において点分析を行った結果、Ｃａが２．０原子％、Ｂａ＋Ｔｉが９８．０原子％の割合であった。ここでいう原子％とは、モル％と同義である。
図４ではバリウム原子を白色、チタン原子を灰色で表示している。ＥＤＳマッピングの結果を示した図５ではＢａの白色のみ表示し、図６ではＣａのみを白色で表示している。
図５と６を比較すると、図６では図５のＢａ位置と重なる位置にＣａが検出されている。このことから、バリウムサイトにカルシウムが固溶していることが確認された。 Example 1
(Barium titanate dispersion preparation process)
A 5-L reaction vessel was charged with 1.3 L of pure water and 1,157 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.), and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution.
0.23 L of titanium tetrachloride solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., Ti equivalent concentration 186 g/L) was mixed with the above barium hydroxide aqueous solution to obtain a barium titanate precursor aqueous slurry with a concentration of 80 g/L in terms of BaTiO 3. The Ba/Ti molar ratio at the end of mixing the barium hydroxide aqueous solution and the titanium tetrachloride solution was 4.0.
(Barium ion removal process)
While stirring the barium titanate precursor slurry with a stirrer, a nitric acid aqueous solution with a concentration of 20% was dropped, the pH of the slurry was adjusted to 11.0, and the pH was maintained for 1 hour. After this, the mixture was filtered and washed with water until the electrical conductivity of the filtrate was 50 μS/cm or less, and a cake was obtained after washing with water. Water was added to the cake to make the liquid volume 1 L, and after washing with water, a barium titanate bulk slurry was obtained. A portion of the slurry obtained above was sampled and dried in a box dryer at 95 ° C., and the Ba/Ti molar ratio was determined by XRF analysis, which was 0.814. The SEM observation result of this barium titanate precursor water slurry is shown in FIG. 1-1. In FIG. 1-1, it was confirmed that there was no particle aggregation in the obtained barium titanate precursor.
(Heat treatment process (drying process))
After the above water washing, 12 g of calcium acetate monohydrate (manufactured by Kanto Chemical Co., Ltd.) and 27 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.) were added to the barium titanate raw material slurry and stirred with a stirrer, then spray-dried at 95°C and crushed in a mortar or the like to obtain a barium calcium titanate precursor powder.
(Heat treatment process (firing process))
20 g of the barium calcium titanate precursor powder was placed in an alumina crucible and heat-treated in an air furnace at 600° C. for 2 hours to obtain a barium calcium titanate solidified material.
(Disintegration process)
15 g of the barium calcium titanate deposit obtained above was placed in an autoclave vessel, 7 g of pure water and 11 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.) were added, and the mixture was hydrothermally treated at 160°C for 24 hours. The contents of the autoclave were allowed to cool to room temperature, and the collected slurry was filtered and washed with water until the electrical conductivity of the filtrate was 50 μS/cm or less, and then dried in a box dryer at 95°C for 6 hours. The dried deposit was crushed in a mortar to obtain barium calcium titanate powder. SEM observation results of the obtained barium calcium titanate are shown in Figure 1-2, HAADF-STEM images are shown in Figures 3 and 4, and EDS mapping results are shown in Figures 5 and 6.
It was confirmed from FIG. 1-2 that the obtained barium calcium titanate was spherical and had a uniform particle size.
As a result of a point analysis performed at the location 01 in the HAADF-STEM image in Figure 3, the ratio of Ca was 2.0 atomic % and Ba + Ti was 98.0 atomic %. The atomic % here is synonymous with mol %.
In Fig. 4, barium atoms are displayed in white and titanium atoms in grey. In Fig. 5, which shows the results of EDS mapping, only Ba is displayed in white, and in Fig. 6, only Ca is displayed in white.
5 and 6, Ca was detected in Fig. 6 at a position overlapping with the Ba position in Fig. 5. This confirmed that calcium was dissolved in the barium site.
実施例２～７
反応に用いた各種成分の種類や量及び反応条件を表１に記載のように変更した以外は実施例１と同様にして実施例２～７を行った。実施例７で得られたチタン酸バリウムカルシウムのＸＲＤ測定結果を図７に示す。
図７のＸＲＤ測定チャートには位相はみられず、純度の高いペロブスカイト型化合物が得られていることが確認された。 Examples 2 to 7
Examples 2 to 7 were carried out in the same manner as Example 1, except that the types and amounts of various components used in the reaction and the reaction conditions were changed as shown in Table 1. The results of XRD measurement of the barium calcium titanate obtained in Example 7 are shown in FIG.
No phase was observed in the XRD measurement chart of FIG. 7, confirming that a highly pure perovskite type compound was obtained.
比較例１
５Ｌ容量の反応容器に純水１．６Ｌと水酸化バリウム八水和物（堺化学工業株式会社製）８６８ｇを入れて加熱し、水酸化バリウム八水和物を水に溶解させて、水酸化バリウム水溶液を調製した。
四塩化チタン溶液（富士フイルム和光純薬株式会社製、Ｔｉ換算で１８６ｇ／Ｌ濃度）０．１７Ｌを上記水酸化バリウム水溶液と混合し、ＢａＴｉＯ３換算で６０ｇ／Ｌ濃度のチタン酸バリウム前駆体水スラリーを得た。水酸化バリウム水溶液と四塩化チタン溶液の混合終了時点でのＢａ／Ｔｉモル比は４．０であった。
得られたチタン酸バリウム前駆体水スラリーのＳＥＭ観察結果を図２－１に示す。図２－１では、実線で囲んだ箇所でチタン酸バリウム前駆体では粒子の凝集があることが確認された。
その後、表１に記載のとおりに各工程を変更した以外は実施例１と同様にして解粒工程まで行い、比較例１のチタン酸バリウムカルシウム粉末を得た。
解粒工程で得られたチタン酸バリウムカルシウムのＳＥＭ観察結果を図２－２に示す。図２－２では、実線で囲んだ箇所でチタン酸バリウムカルシウムの粗大粒子が観察され、粒子径のバラつきがあることが確認された。 Comparative Example 1
A 5-L reaction vessel was charged with 1.6 L of pure water and 868 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.), and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution.
0.17 L of titanium tetrachloride solution (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., Ti equivalent concentration 186 g/L) was mixed with the above barium hydroxide aqueous solution to obtain a barium titanate precursor aqueous slurry with a concentration of 60 g/L in terms of BaTiO 3. The Ba/Ti molar ratio at the end of mixing the barium hydroxide aqueous solution and the titanium tetrachloride solution was 4.0.
The results of SEM observation of the obtained barium titanate precursor aqueous slurry are shown in Fig. 2-1. In Fig. 2-1, it was confirmed that particles of the barium titanate precursor were aggregated in the area surrounded by a solid line.
Thereafter, the same procedures as in Example 1 were carried out up to the deagglomeration step, except that each step was changed as shown in Table 1, to obtain a barium calcium titanate powder of Comparative Example 1.
The results of SEM observation of the barium calcium titanate obtained in the deagglomeration process are shown in Figure 2-2. In Figure 2-2, coarse particles of barium calcium titanate were observed in the area surrounded by a solid line, and it was confirmed that the particle size varied.
比較例２～３
反応に用いた成分の種類や量及び反応条件を表１に記載のように変更した以外は比較例１と同様にして比較例２～３を行った。 Comparative Examples 2 to 3
Comparative Examples 2 and 3 were carried out in the same manner as Comparative Example 1, except that the types and amounts of the components used in the reaction and the reaction conditions were changed as shown in Table 1.
比較例４
（チタン酸バリウム分散液調製工程）
５Ｌ容量の反応容器に純水２．１Ｌと水酸化バリウム八水和物（堺化学工業株式会社製）９０９ｇを入れて加熱し、水酸化バリウム八水和物を水に溶解させて、水酸化バリウム水溶液を調製した。
水酸化チタンの水スラリー（堺化学工業株式会社製、Ｔｉ換算で１８４ｇ／Ｌ濃度）０．５０Ｌを上記水酸化バリウム水溶液と混合し、ＢａＴｉＯ３換算で１５９ｇ／Ｌ濃度のチタン酸バリウム水スラリーを得た。水酸化バリウム水溶液に水酸化チタンの水スラリーを加え終わった時点でのＢａ／Ｔｉモル比は２．２であった。
上記チタン酸バリウム水スラリーをオートクレーブ容器に入れ、１００℃で６時間水熱処理した。オートクレーブ内容物を室温まで放冷し、チタン酸バリウム前駆体スラリーを得た。
（脱バリウムイオン処理工程）
上記チタン酸バリウム前駆体スラリーを撹拌機で撹拌しながら、濃度２０％の硝酸水溶液を滴下し、スラリーｐＨが７．０になるように調整し、ｐＨを１時間維持させた。この後、濾過水洗し、濾液の電気伝導度が１００μＳ／ｃｍ以下になるまで水洗を行い、水洗後のケーキを得た。このケーキに水を加えて液量を１Ｌにし、水洗後チタン酸バリウム前駆体スラリーを得た。上記で得られたスラリーから、一部サンプリングを行い、９５℃の箱型乾燥機で乾燥させた後、ＸＲＦ分析にてＢａ／Ｔｉモル比を求めたところ、０．９０２であった。
（熱処理工程（乾燥工程））
上記水洗後チタン酸バリウム前駆体スラリーに酢酸カルシウム１水和物（関東化学株式会社製）１１ｇを入れて撹拌機で撹拌した後、９５℃で噴霧乾燥させ、乳鉢等で解砕することで、チタン酸バリウムカルシウム前駆体粉末を得た。
（熱処理工程（焼成工程））
上記チタン酸バリウムカルシウム前駆体粉末１０ｇをアルミナ製ルツボに入れて、大気焼成炉にて６００℃で２時間熱処理させることでチタン酸バリウムカルシウム固着物を得た。
（解粒工程）
上記で得られたチタン酸バリウムカルシウム固着物１０ｇをオートクレーブ容器に入れ、純水５０ｇと水酸化バリウム八水和物（堺化学工業株式会社製）２９ｇを加え、１６０℃で２４時間水熱処理した。オートクレーブ内容物を室温まで放冷し、回収したスラリーを濾過水洗し、濾液の電気伝導度が５０μＳ／ｃｍ以下になるまで洗浄を行った後、９５℃の箱型乾燥機で６時間乾燥させた。乾燥後の固着物を乳鉢で解砕することでチタン酸バリウムカルシウム粉末を得た。 Comparative Example 4
(Barium titanate dispersion preparation process)
2.1 L of pure water and 909 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.) were placed in a 5 L reaction vessel and heated to dissolve the barium hydroxide octahydrate in the water, thereby preparing an aqueous barium hydroxide solution.
0.50 L of an aqueous titanium hydroxide slurry (manufactured by Sakai Chemical Industry Co., Ltd., concentration of 184 g/L calculated as Ti) was mixed with the above aqueous barium hydroxide solution to obtain an aqueous barium titanate slurry having a concentration of 159 g/L calculated as BaTiO3. The Ba/Ti molar ratio was 2.2 when the aqueous titanium hydroxide slurry was added to the aqueous barium hydroxide solution.
The above barium titanate water slurry was placed in an autoclave vessel and subjected to hydrothermal treatment for 6 hours at 100° C. The contents of the autoclave were allowed to cool to room temperature to obtain a barium titanate precursor slurry.
(Barium ion removal process)
While stirring the barium titanate precursor slurry with a stirrer, a nitric acid aqueous solution with a concentration of 20% was dropped to adjust the slurry pH to 7.0, and the pH was maintained for 1 hour. After this, the mixture was filtered and washed with water until the electrical conductivity of the filtrate was 100 μS/cm or less, and a cake was obtained after washing with water. Water was added to the cake to make the liquid volume 1 L, and a barium titanate precursor slurry was obtained after washing with water. A portion of the slurry obtained above was sampled and dried in a box dryer at 95 ° C., and the Ba/Ti molar ratio was determined by XRF analysis to be 0.902.
(Heat treatment process (drying process))
After the water washing, 11 g of calcium acetate monohydrate (manufactured by Kanto Chemical Co., Ltd.) was added to the barium titanate precursor slurry and stirred with a stirrer, then spray-dried at 95°C and crushed in a mortar or the like to obtain a barium calcium titanate precursor powder.
(Heat treatment process (firing process))
10 g of the barium calcium titanate precursor powder was placed in an alumina crucible and heat-treated in an air furnace at 600° C. for 2 hours to obtain a barium calcium titanate solidified material.
(Disintegration process)
10 g of the barium calcium titanate deposit obtained above was placed in an autoclave container, 50 g of pure water and 29 g of barium hydroxide octahydrate (manufactured by Sakai Chemical Industry Co., Ltd.) were added, and the mixture was hydrothermally treated at 160° C. for 24 hours. The contents of the autoclave were allowed to cool to room temperature, and the collected slurry was filtered and washed with water until the electrical conductivity of the filtrate was 50 μS/cm or less, and then dried in a box dryer at 95° C. for 6 hours. The dried deposit was crushed in a mortar to obtain barium calcium titanate powder.
比較例５
反応に用いた成分の種類や量及び反応条件を表１に記載のように変更した以外は比較例４と同様にして比較例５を行った。 Comparative Example 5
Comparative Example 5 was carried out in the same manner as Comparative Example 4, except that the types and amounts of the components used in the reaction and the reaction conditions were changed as shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
実施例１～７、比較例１～５で得られたチタン酸バリウムカルシウム（ＢＣＴ）の各種測定結果を表２に示す。 The various measurement results for the barium calcium titanate (BCT) obtained in Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
表１、２に示されるとおり、実施例１～７ではいずれもＣＶ値が２０％以下のチタン酸バリウムカルシウムが得られる結果となった。一方、比較例１～５では得られたチタン酸バリウムカルシウムはいずれもＣＶ値が２０％より大きいものであった。
これらの結果から、本発明のペロブスカイト型化合物の製造方法を用いることで、粒子サイズの均一性が高いチタン酸バリウムカルシウムを得られることが確認された。 As shown in Tables 1 and 2, barium calcium titanate having a CV value of 20% or less was obtained in all of Examples 1 to 7. On the other hand, the barium calcium titanate obtained in Comparative Examples 1 to 5 all had a CV value of more than 20%.
From these results, it was confirmed that by using the method for producing a perovskite compound of the present invention, barium calcium titanate having a high uniformity in particle size can be obtained.

Claims (3)

  1. 下記一般式（１）：
    Ｂａ（１－ｘ）ＡｘＴｉＯ３　　　（１）
    （式中、ＡはＣａ又はＳｒを表す。ｘは、０．００＜ｘ≦０．３０の数である。）で表され、
    走査電子顕微鏡観察から得られる平均粒子径（円相当径）に対する粒子径の標準偏差の割合（粒子径の標準偏差／平均粒子径×１００）で表されるＣＶ値が２０％以下であることを特徴とするペロブスカイト型化合物。     The following general formula (1):
    Ba (1-x) A x TiO 3 (1)
    (In the formula, A represents Ca or Sr, and x is a number satisfying 0.00<x≦0.30),
    A perovskite compound characterized in that the CV value, which is expressed as the ratio of the standard deviation of particle diameter to the average particle diameter (equivalent circle diameter) obtained by observation with a scanning electron microscope (standard deviation of particle diameter/average particle diameter x 100), is 20% or less.
  2. ＢＥＴ比表面積が５～７０ｍ２／ｇであることを特徴とする請求項１に記載のペロブスカイト型化合物。 2. The perovskite compound according to claim 1, characterized in that it has a BET specific surface area of 5 to 70 m 2 /g.
  3. バリウム化合物とチタン化合物水溶液とを混合してチタン酸バリウム分散液を得るチタン酸バリウム分散液調製工程と、
    チタン酸バリウム分散液調製工程で得られたチタン酸バリウム分散液を洗浄処理してチタン元素に対するバリウム元素のモル比が１．００未満であるチタン酸バリウムを得る脱バリウムイオン処理工程と、
    脱バリウムイオン処理工程で得られたチタン酸バリウムとカルシウム塩又はストロンチウム塩とを混合し、熱処理する熱処理工程と、
    熱処理工程で得られた化合物を溶媒中で加熱して解粒する解粒工程とを含み、
    チタン酸バリウム分散液調製工程において、バリウム化合物中のバリウム元素とチタン化合物水溶液中のチタン元素とのモル比（Ｂａ／Ｔｉ）が４．５以上となるようにバリウム化合物とチタン化合物水溶液とを用いるか、脱バリウムイオン処理工程に用いるチタン酸バリウム分散液中のチタン酸バリウム濃度を６５ｇ／Ｌ以上とするかの少なくとも一方を行う
    ことを特徴とするペロブスカイト型化合物の製造方法。     a barium titanate dispersion preparation step of mixing a barium compound and an aqueous titanium compound solution to obtain a barium titanate dispersion;
    a barium ion removing process for washing the barium titanate dispersion obtained in the barium titanate dispersion preparation process to obtain barium titanate having a molar ratio of barium element to titanium element of less than 1.00;
    a heat treatment step of mixing the barium titanate obtained in the barium ion removing treatment step with a calcium salt or a strontium salt and heat treating the mixture;
    A disintegration step of heating the compound obtained in the heat treatment step in a solvent to disintegrate the compound,
    A method for producing a perovskite compound, characterized in that in a barium titanate dispersion preparation step, a barium compound and an aqueous titanium compound solution are used so that the molar ratio (Ba/Ti) of the barium element in the barium compound to the titanium element in the aqueous titanium compound solution is 4.5 or more, or the barium titanate concentration in the barium titanate dispersion used in the barium ion debarium treatment step is 65 g/L or more.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06305729A (en) * 1993-04-19 1994-11-01 Titan Kogyo Kk Fine powder of perovskite type compound and its production
JPH07277710A (en) * 1994-04-05 1995-10-24 Kyowa Chem Ind Co Ltd Production of perovskite-type multiple oxide powder
JP2006089368A (en) * 2004-08-27 2006-04-06 Showa Denko Kk Barium calcium titanate, production process thereof and capacitor
US20070202036A1 (en) * 2004-04-07 2007-08-30 Nathalie Jongen Production Of Barium Titanate Compounds
WO2021199702A1 (en) * 2020-03-30 2021-10-07 堺化学工業株式会社 Method for producing perovskite compound, and perovskite compound

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06305729A (en) * 1993-04-19 1994-11-01 Titan Kogyo Kk Fine powder of perovskite type compound and its production
JPH07277710A (en) * 1994-04-05 1995-10-24 Kyowa Chem Ind Co Ltd Production of perovskite-type multiple oxide powder
US20070202036A1 (en) * 2004-04-07 2007-08-30 Nathalie Jongen Production Of Barium Titanate Compounds
JP2006089368A (en) * 2004-08-27 2006-04-06 Showa Denko Kk Barium calcium titanate, production process thereof and capacitor
WO2021199702A1 (en) * 2020-03-30 2021-10-07 堺化学工業株式会社 Method for producing perovskite compound, and perovskite compound

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