JP2012211046A - Method for producing barium titanate powder, and method for producing electronic component using the barium titanate powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing barium titanate powder which can control a particle diameter within 40 nm-300 nm in a solid phase method, has sharp particle size distribution, and high crystallinity and anisotropy, greatly reduce holes (defects) in particles to none or very few, and can control Ba/Ti as well, and to provide a method for producing an electronic component using the barium titanate powder.SOLUTION: The method for producing barium titanate powder using an aqueous titanium solution and barium salt powder as starting raw materials includes: a gelling step of mixing and gelling the starting raw materials; a drying step of drying the gelled mixture; a heat treatment step of heating the dried powder to generate barium titanate particles; and a separation step of separating the barium titanate particles from the heat-treated powder.

Description

  The present invention relates to a method for producing a barium titanate powder, a method for producing a barium titanate powder, and an electronic component. The present invention relates to perovskite-type oxide nanoparticles (dielectric particles) that are absent or very few.

  The technology for synthesizing oxide particles by a solid phase method has been developed for a long time, and the fine particle production methods are roughly classified into chemical methods and physical methods. As a currently established technique, a chemical method includes a crystallization method, which utilizes a phase transition phenomenon from a solid phase to a new solid phase. The physical method is also called a built-down method, in which mechanical pulverization is repeated with a pulverizer to pulverize the particles.

  However, although it is generally said that particles with good crystallinity can be synthesized by crystallization methods, it is not suitable for dealing with nanoparticle diameters or for synthesizing particles with a sharp particle size distribution. Barium titanate synthesis method that satisfies the particle size and particle size distribution required for barium titanate used in the field of multilayer ceramic capacitors (MLCC), which has been multilayered, has become the mainstream. Absent.

  In addition, the solid phase method to make fine particles by mechanical pulverization is a problem of contamination due to pulverization, a problem of chipping of the base material, difficulty in pulverization to the nanoparticle diameter, and a technology capable of sharply pulverizing the particle size distribution has not been established. It is not used as a method for producing fine powder of barium titanate.

  In addition to solid-phase reactions, hydrothermal synthesis and oxalate methods are used as barium titanate synthesis methods. However, hydrothermal synthesis has problems of intraparticle defects and pores, and the life of MLCC It is not preferable as a method for synthesizing barium titanate that can improve the characteristics. In addition, the oxalate method is a liquid phase method for raw material synthesis and a target powder synthesis is a solid phase method, and there are relatively few defects and pores in the particles. The crystallinity is moderate, and each has its own drawbacks.

  Therefore, if the chemical size of the solid-phase method has a sharp particle size distribution and a nano-order particle size of 40 nm to 300 nm, improvement in characteristics from the MLCC substrate can be expected. Improvements are being made.

  Under these circumstances, in order to solve these problems, a method of obtaining submicron particles of about 200 nm by calcining using fine powders of titanium oxide and barium carbonate as raw powders, and blending of raw powders And a method for producing a barium titanate powder that obtains particles of about 100 nm by optimizing calcination conditions (temperature, atmosphere) (for example, Patent Documents 1 and 2).

JP 2003-2739 A JP 2008-115042 A

  However, the method for producing barium titanate powder as proposed in Patent Documents 1 and 2 does not solve the fundamental problem of the solid-phase chemical method, and has a sharp particle size distribution. However, if the calcination temperature is lowered and the particle size is reduced, problems such as decrease in crystallinity and anisotropy occur, and the advantage of the solid phase method is lost.

  The present invention has been made in view of the above problems. In the solid phase method, the particle diameter can be controlled from 40 nm to 300 nm, the particle size distribution is sharp, the crystallinity and the anisotropy are high, and the inner space of the particle is empty. It is an object of the present invention to provide a method for producing a barium titanate powder, a method for producing a barium titanate powder, and an electronic component that have no or very few holes (defects) and can control Ba / Ti.

  In order to solve the above-described problems and achieve the object, the method for producing a barium titanate powder according to the present invention is a gelation method in which a titanium aqueous solution and a barium salt powder are used as starting materials, and the starting materials are mixed and gelled. A step of drying the gelled mixture, a heat treatment step of heat-treating the dry powder to produce barium titanate particles, and a separation step of separating the barium titanate particles from the heat-treated powder. It is characterized by that. According to the present invention, it is possible to produce a barium titanate powder having a nano-order particle size, a sharp particle size distribution, high crystallinity and anisotropy, and no intrapore (defect).

  In the present invention, the aqueous titanium solution is preferably a mixed aqueous solution of a water-soluble titanium raw material and an acidic chelating agent. By using a water-soluble Ti raw material and further gelling, a more uniform dispersion state can be maintained until the drying stage. Moreover, precipitation of a water-soluble titanium raw material can be suppressed by using an acidic chelating agent, and hydrolysis of the titanium raw material at the time of mixing barium salt powder can be suppressed.

  In the present invention, the barium salt powder is preferably mixed in a molar ratio of 3 times or more with respect to the titanium raw material. The Ba / Ti ratio during mixing has an effect on the particle size and particle size distribution. When the Ba / Ti ratio is low (1 or more and 2 or less), the thermal diffusion length at the time of calcining becomes long, the titanium raw material is aggregated, the grain growth reaction is likely to proceed, the particles are enlarged, and the particle size distribution is deteriorated. When the Ba / Ti ratio is high, the barrier of the barium compound generated before the reaction is increased, the grain growth reaction is difficult to proceed, the particle size is decreased, and the particle size distribution is improved. Therefore, the particle diameter and particle size distribution of the barium titanate powder at the time of mixing can be suitably maintained by setting the Ba / Ti ratio to 3 times or more.

  In the present invention, the mixed aqueous solution is preferably a saturated aqueous solution in which barium salt powder has reached saturation solubility. The concentration of barium in the mixed aqueous solution has an effect on the particle size and particle size distribution. If the concentration of barium is low, the amount of barium dissolved in the water in the gel is small, so the thermal diffusion length during heat treatment becomes long, the titanium raw material agglomerates, and the particle growth reaction tends to proceed, resulting in larger particles. At the same time, the particle size distribution becomes worse. When the barium concentration is saturated, the amount of barium dissolved in the water in the gel is maximized, which increases the barrier of the barium compound produced before the reaction, making it difficult for the grain growth reaction to proceed. As the diameter decreases, the particle size distribution is best. Therefore, the particle diameter and particle size distribution of the barium titanate powder at the time of mixing can be suitably maintained by making barium in the mixed aqueous solution saturated.

  In the present invention, the dried powder that has undergone the drying step is preferably in a state in which barium salt particles are the main particles, and one or more titanium oxides are dispersed without contacting each other. By the drying process, barium salt particles are used as the main particles, and one or more titanium oxides are produced in a desired size and dispersed without contacting each other. A method such as vat drying is not preferable because barium dissolved in water in the gel gradually precipitates as the water evaporates, making it impossible to obtain the desired dry powder. Necking of barium titanate during heat treatment by using barium salt particles as the main particles, in which one or more aggregates of titanium oxide are dispersed in a desired size and not in contact with each other And the particle size and particle size distribution can be suitably maintained.

  In the present invention, it is preferable that the barium salt becomes a basic barium compound by the heat treatment step. By the heat treatment step, the barium salt becomes a basic barium compound, so that excess barium can be easily dissolved.

  The heat treatment temperature in the heat treatment step is preferably 500 ° C. or higher and lower than 800 ° C. When the reaction temperature is increased, crystalline barium carbonate is formed. Therefore, the transformation of the barium compound facilitates the movement and necking of the titanium compound, and also eliminates the barrier effect of suppressing the necking of the barium compound and increases the particle size. The calcining temperature is preferably 500 ° C. or higher and lower than 800 ° C.

  In the present invention, the separation step mixes the powder after heat treatment with a solvent, dissolves the basic barium salt, which is an unreacted barium compound as an excess, and forms the titanic acid from the heat treated powder after heat treatment. It is preferable to have a step of separating the barium particles. By this separation step, barium titanate having a suitably maintained particle size and particle size distribution can be obtained.

In order to solve the above-described problems and achieve the object, the barium titanate powder according to the present invention is a perovskite type barium titanate powder produced by the method for producing a barium titanate powder described above. A barium titanate powder that is an aggregate of barium titanate particles having a crystal structure, having a (100) plane as a main surface, and a c-axis lattice constant and an a-axis lattice constant in the perovskite crystal structure, The c / a indicating the ratio is 1.00 or more, the half width of the (111) peak observed by X-ray diffraction is 0.250 or less, and the specific surface area by the BET method is 3.3 m ² / g or more. and a 25 m ² / g or less, the particle size of which cumulative number is 10% D10, the particle size of which cumulative number is 50% D50 and cumulative number has a D90 particle size at 90% The case, characterized in that it (D90-D10) / D50 of 2.0 or less. By using the barium titanate powder obtained by this manufacturing method, a thin-layer multilayer small-capacity multilayer ceramic capacitor having high reliability can be obtained.

  In order to solve the above-described problems and achieve the object, an electronic component manufacturing method according to the present invention is a method of manufacturing an electronic component having a dielectric layer and an electrode layer, the titanic acid described above. It has a pre-firing dielectric layer forming step for forming a pre-firing dielectric layer containing barium powder, and a firing step for firing the pre-firing dielectric layer. As a result, the dielectric layer is produced using the barium titanate powder obtained by using the method for producing a barium titanate powder according to the present invention. An electronic component can be obtained.

  According to the present invention, in the solid phase method, the particle size can be controlled from 40 nm to 300 nm, the particle size distribution is sharp, the crystallinity and anisotropy are high, and there are no or very few vacancies (defects) in the particles. , Barium titanate powder capable of controlling Ba / Ti can be obtained.

FIG. 1 is a flowchart showing an example of a method for producing a barium titanate powder according to the present embodiment. FIG. 2 is a diagram schematically showing the state of the Ba / Ti gel. FIG. 3 is a schematic cross-sectional view showing the mixture after drying. FIG. 4 is a schematic cross-sectional view showing the heat-treated powder after heat treatment. FIG. 5 is a conceptual cross-sectional view schematically showing one embodiment of a ceramic capacitor. FIG. 6 is a diagram showing an XRD result of the mixture after the heat treatment. FIG. 7 is a diagram showing an XRD result of a sample obtained by removing excess barium from the heat-treated mixture. FIG. 8 is an SEM photograph of the mixture after the heat treatment. FIG. 9 is an SEM photograph of a sample obtained by removing excess barium from the heat-treated mixture. FIG. 10 is another SEM photograph of the sample from which excess barium has been removed from the heat-treated mixture. FIG. 11 is a TEM photograph of sample No. 5 barium titanate powder. FIG. 12 is a diagram showing an XRD chart of sample number 25. FIG. 13 is a photograph of FE-SEM of sample number 26.

  Hereinafter, embodiments (hereinafter referred to as embodiments) and examples of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the embodiment and the Example for implementing the following invention. In addition, constituent elements in the following embodiments and examples include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments and examples may be appropriately combined or may be appropriately selected and used.

<Barium titanate powder>
The barium titanate powder according to the present embodiment is an aggregate of barium titanate particles having a perovskite crystal structure, and Ba occupies A site and Ti occupies B site in the crystal structure. In the present embodiment, the barium (Ba) / titanium (Ti) ratio indicating the molar ratio of the atoms occupying the A site and the atoms occupying the B site is preferably 0.980 to 1.010, more preferably Is in the range of 0.990 to 1.004. This Ba / Ti ratio is preferably adjusted in the above range depending on the application of the powder. In the present embodiment, the Ba / Ti ratio can be adjusted in the method for producing barium titanate powder described below.

  The perovskite crystal structure changes with temperature, and becomes a tetragonal system at room temperature below the Curie point, and becomes a cubic system above the Curie point. In the cubic system, each crystal axis (a axis, b axis, c axis) has the same lattice constant, but in the tetragonal system, the lattice constant of one axis (c axis) is the other axis (a axis). (= B axis)) is longer than the lattice constant.

  In the present embodiment, considering the particle diameter of barium titanate, c / a indicating the ratio of the c-axis lattice constant to the a-axis lattice constant is 1.0045 or more, preferably 1.0070 or more, more preferably 1.0090 or more. This c / a is an index of anisotropy of barium titanate, and is preferably higher from the viewpoint of obtaining a high dielectric constant.

  Note that the c / a of all barium titanate particles in the barium titanate powder need not satisfy the above range. That is, for example, tetragonal barium titanate particles and cubic barium titanate particles may coexist in the barium titanate powder. If it is in range.

  In this embodiment, the half width of the (111) peak obtained by X-ray diffraction for the barium titanate powder is 0.25 or less, preferably greater than 0 and less than 0.200, more preferably greater than 0 and less than 0.150. It is. The half width is an index of the crystallinity of barium titanate, and is preferably smaller from the viewpoint of suppressing grain growth and obtaining a high dielectric constant.

The barium titanate powder according to this embodiment has a specific surface area measured by the BET method of 3.3 m ² / g to 25 m ² / g. The specific surface area of powder and the average particle diameter are in inverse proportion, and when the above specific surface area is converted into the average particle diameter of powder, the average particle diameter is 40 nm or more and 300 nm or less, and can be arbitrarily adjusted.

  Further, in the barium titanate powder according to the present embodiment, the particle diameter at which the cumulative number is 10% is D10, the particle diameter at which the cumulative number is 50% is D50, and the particle diameter at which the cumulative number is 90% is D90. , (D90-D10) / D50 is 2.0 or less, preferably 1.8 or less, more preferably 1.5 or less. This (D90-D10) / D50 shows the variation of the particle diameter with reference to D50, and is an indicator of whether the particle size distribution is broad or sharp. The barium titanate powder according to this embodiment has a small difference between D90 and D10 and a sharp particle size distribution.

  In addition, although it does not restrict | limit in particular as a method of measuring particle diameter, In this embodiment, a field emission scanning electron microscope (FE-SEM), a transmission electron microscope (TEM), etc. It is preferable to measure the particle diameter of each particle.

  From the above, the barium titanate powder according to the present embodiment has high crystallinity and anisotropy, has a particle size on the order of nanometers, has a sharp particle size distribution, and reduces pores (defects) in the particles. , Ba / Ti controlled powder.

  By using barium titanate powder having such characteristics as a raw material, for example, even when the dielectric layer of a multilayer electronic component is thinned, a plurality of barium titanate particles can be arranged between the layers. It is possible to provide a ceramic electronic component having a high relative dielectric constant while ensuring sufficient reliability such as a high temperature load life.

<Method for producing barium titanate powder>
Next, an example of a method for producing the barium titanate powder according to the present embodiment will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of a method for producing a barium titanate powder according to the present embodiment.

  As shown in FIG. 1, a titanium aqueous solution, a chelating agent aqueous solution, and a Ba salt are prepared as starting materials (raw material preparation step: step S11). In this embodiment, Ba salt powder is used as the Ba salt.

  As the Ti raw material in the titanium aqueous solution, a water-soluble Ti raw material is used. The water-soluble Ti raw material is preferably a titanium chloride solution, a titanium chloride aqueous solution, or a peroxytitanic acid aqueous solution, but in this embodiment, a titanium chloride aqueous solution is used. The Ti concentration in the aqueous solution is not particularly limited, but is preferably 10% by mass or more and 20% by mass or less from the viewpoint of handling. If the concentration is too low, the aqueous titanium solution is unstable, and hydroxide precipitates.

  A water-soluble barium salt is used as the Ba raw material. The Ba salt is not particularly limited as long as it is water-soluble. Specifically, barium chloride, barium nitrate, barium formate, barium acetate, barium lactate, barium perchlorate, barium fluoride, barium hydroxide, barium oxalate, barium chlorate, barium iodate, barium iodide, odor Barium fluoride, barium carbonate and the like. These may be used in combination. From the viewpoint of ease of handling and solubility in water, barium carbonate, barium chloride, barium nitrate, and barium acetate are more preferable. In this embodiment, barium acetate is used.

  The concentration of the Ba salt in the mixed aqueous solution was a saturated aqueous solution. The purpose of this is to maximize the abundance of Ba ions per unit volume by being saturated, and prevent aggregation of Ti in the mixture.

  The chelating agent is used to stabilize the water-soluble Ti raw material. The chelating agent needs to be an acidic chelating agent and is not particularly limited as long as the aqueous solution is acidic. By using an acidic chelating agent, precipitation of a water-soluble Ti raw material can be suppressed, and hydrolysis of the Ti raw material during mixing of the Ba salt aqueous solution can be suppressed. If an alkaline chelating agent is used, it cannot be used because Ti hydroxide precipitates during mixing. Specific examples of the carboxylic acid-based chelating agent include tartaric acid, malic acid, citric acid, and gluconic acid. In this embodiment, citric acid was used.

  The concentration of the chelating agent aqueous solution is not particularly limited as long as it is not higher than the solubility of the aqueous solution. This time, a 50% by mass aqueous citric acid solution was prepared and used.

  Next, as shown in the flowchart of FIG. 1, the titanium chloride aqueous solution and the citric acid aqueous solution prepared above are mixed to produce a titanium / citric acid aqueous solution (mixed aqueous solution production step: step S12).

  While this aqueous solution is vigorously stirred, the barium acetate powder is mixed therein and gelled (gelation step: step S13). FIG. 2 is a diagram schematically showing the state of the Ba / Ti gel. As shown in FIG. 2, a large number of barium ions 12, a titanium compound 13, and citric acid 14 are scattered (dispersed) in the water 11, and the titanium compound 13 and the citric acid 14 are hydrogen bonded (FIG. 2). Middle, broken line part). By using a water-soluble Ti raw material and further gelling, a more uniform dispersion state can be maintained until the drying stage.

  The titanium / citric acid / barium aqueous solution, which is an aqueous solution at the initial stage of mixing, also precipitates as Ti becomes a hydroxide when the pH increases in the middle of dropping. Since this hydroxide gel contains a large amount of moisture, it contains a large amount of barium ions.

  The mixing speed of the barium salt powder is not particularly limited, but in the present embodiment, the total amount is preferably supplied for 15 minutes to 45 minutes.

  The mixing ratio (Ba / Ti ratio) of Ba and Ti in the titanium / citric acid / barium slurry (gel) is preferably 3 or more and 10 or less, more preferably 3 or more and 5 or less. That is, the Ba / Ti ratio at the time of mixing has an effect on the particle size and particle size distribution. When the Ba / Ti ratio is low (for example, 1 or more and 2 or less), the thermal diffusion length at the time of calcining becomes long, the titanium raw material aggregates, the grain growth reaction easily proceeds, the particles become large, and the particle size distribution becomes large. Deteriorate. Further, when the Ba / Ti ratio is high (for example, larger than 5), the barrier of the barium compound generated before the reaction becomes large. Therefore, by setting the Ba / Ti ratio within the above range, titanium hydroxide from the titanium aqueous solution is precipitated in a state where Ba is present in excess of Ti. This shortens the thermal diffusion length, makes it difficult for the particles to fuse with each other, and improves the particle size distribution. By doing so, a large amount of barium ions are included in the titanium hydroxide gel, and a large amount of barium ions are also present in water, so that in the drying step described later, When the medium and the solvent are removed, it is possible to obtain a mixture in which the titanium oxide particles are dispersed in the Ba salt particles and the titanium oxide particles are not in contact with each other.

  If the Ba / Ti ratio is too small, for example, 1 or more and less than 2, not only will the amount of barium ions contained in the precipitated titanium hydroxide be reduced, but also the amount of barium ions dissolved in water will be reduced, and after drying. The distance between titanium oxide particles in this mixture tends to be short, and necking of barium titanate produced in the heat treatment step described later tends to occur. On the other hand, if the Ba / Ti ratio is too large, the titanium concentration becomes thin and the productivity is lowered. Moreover, the cost at the time of a washing | cleaning becomes a big demerit.

  Further, in a mixture containing a plurality of titanium oxide particles and a plurality of barium salt particles, one or more titanium oxide particles are scattered (dispersed) in one barium salt particle. In this embodiment, barium acetate powder is mixed with an aqueous solution obtained by mixing an aqueous solution of titanium chloride and an aqueous solution of citric acid and gelled to produce a mixture titanium / citric acid / barium slurry (gel). In the embodiment, the method for producing the mixture is not particularly limited to this, and a mixture containing a plurality of titanium oxide particles and a plurality of barium salt particles may be produced by another method. .

  After the mixing of the barium salt powder, the mixture was stirred for about 3 hours to adjust the pH of the titanium / citric acid / barium slurry (gel) (pH adjustment step: step S14). Although the stirring time is not particularly limited, it is preferably performed for 1 hour or more and 5 hours or less from the viewpoint of stabilization of pH (gel stabilization).

  The pH of the titanium / citric acid / barium slurry (gel) is adjusted according to the target particle size. The pH of the titanium / citric acid / barium slurry (gel) is preferably controlled between 2 and 5, for example, and more preferably 2 and 4 or less. If the desired pH is not reached, the pH of the titanium / citric acid / barium slurry (gel) can be adjusted with hydrochloric acid, acetic acid or an acidic chelating agent, depending on the ratio of Ba / Ti. In this embodiment, it is preferable to use hydrochloric acid. The gel state of titanium hydroxide generated in the middle stage of barium salt powder mixing can be controlled by the pH of the slurry, and the particle size of the target powder can be controlled. That is, the pH of the barium / titanium slurry (gel) is a factor that controls the size of titanium core particles generated during the addition of barium, and this pH control is a parameter for obtaining dielectric particles having a desired particle size. It is.

  Next, the liquid component is removed from the titanium / citric acid / barium slurry (gel) and dried (drying step: step S15). The method of removing the liquid component and drying needs to be uniform, and the method of removing and drying the liquid component includes a titanium hydroxide gel containing barium ions and a uniform liquid component from barium ions ( The method is not particularly limited as long as it can be removed rapidly, and for example, a drying method using spray drying, slurry drying, freeze drying, spray pyrolysis apparatus, or the like can be used. Since the purpose of the drying process is uniform drying, instantaneous drying is preferred. With slow drying, crystallization of the Ba salt occurs gradually, so that uniform Ti—Ba dry powder cannot be obtained. A spray dryer or a slurry dryer can be preferably used. Further, a spray pyrolysis apparatus and a freeze dryer that can perform calcination at the same time can also be suitably used. Moreover, a spray dryer, a spray pyrolysis apparatus, and a freeze dryer are suitable from the viewpoint of contamination-free. Freeze dryers are not preferred for use in solutions that cannot be flash frozen. Therefore, it is preferable to dry using a spray dryer or a spray pyrolysis apparatus.

  In this embodiment, it is dried by spray drying. By performing spray drying, the liquid component in the slurry (gel) is instantaneously and uniformly removed, and particles having a predetermined diameter are obtained. At this time, the barium ions encapsulated in the titanium hydroxide gel are dried while maintaining the state, the barium ions are in the form of Ba salts, and the barium ions dissolved in the water are also in the form of Ba salts and are dried. Form particles. The titanium hydroxide gel becomes titanium oxide by the drying process (step S15), and is more strongly fixed in the dry particles by the Ba salt in which the barium ions contained therein are changed. As a result, as shown in FIG. 3, dry powder (mixture) 17 containing Ba salt particles 15 and titanium oxide particles 16 is obtained. In this dry powder (mixture) 17, a large number of titanium oxide particles 16 are scattered (dispersed) in Ba salt particles 15. In the dry powder 17 obtained by spray drying, Ba salt particles 15 are attached around the titanium oxide particles 16, and the titanium oxide particles 16 are not in contact with each other.

  In this embodiment, the particle diameter of the dry powder 17 is preferably 100 μm or less, more preferably 80 μm or more and 30 μm or less.

Next, as shown in the flowchart of FIG. 1, the obtained dry powder is heat-treated (heat treatment step: step S16). In this heat treatment step (step S16), as shown in FIG. 3, first, a reaction occurs in which barium oxide (partial barium carbonate) is generated from the Ba salt particles 15, and then the generated barium oxide (partial barium carbonate) is produced. A solid phase reaction occurs between the titanium oxide particles 16 and barium titanate (BaTiO ₃ ).

Here, as shown in FIG. 3, the dried powder 17 obtained above is in a state where titanium oxide particles 16 having a uniform particle diameter are scattered in the Ba salt particles 15. Accordingly, the titanium oxide particles 16 and the generated barium oxide (partially barium carbonate) come into contact with each other. When the dry powder 17 is heat-treated, the solid phase reaction between the titanium oxide particles 16 and the Ba salt particles 15 occurs. As shown in FIG. 4, barium titanate (BaTiO ₃ ) particles 19 are generated in the heat-treated powder 18. Moreover, even if the barium titanate particles 19 are generated, the barium titanate particles 19 are in contact with each other because the barium oxide (partially barium carbonate) 20 exists between the barium titanate particles 19 as a barrier. Absent. As a result, since the binding of the barium titanate particles 19 is suppressed, the barium titanate particles 19 maintained in a state where the particle diameter is small are obtained.

In addition, when titanium oxide particles other than titanium oxide (TiO ₂ ) particles 16 are present in the mixture after drying, a reaction for generating titanium dioxide from titanium oxide occurs in the heat treatment step. .

  The heat treatment temperature (calcination temperature) in the heat treatment step (step S16) is preferably 500 ° C. or higher and 800 ° C. or lower, more preferably 650 ° C. or higher and 750 ° C. or lower, which is lower than the normal heat treatment temperature during the solid phase reaction. ing. In the present embodiment, as described above, the solid phase reaction proceeds in all directions, and the state of the titanium oxide particles is unstable. Therefore, even if the heat treatment temperature is lower than usual, the solid phase reaction is sufficiently and quickly performed. Can be advanced. By heat treatment (calcination), the Ba salt becomes barium oxide, partially becomes barium carbonate, the titanium salt becomes an oxide, and Ti and Ba react to become barium titanate. The particle size and particle size distribution can be controlled by the reaction temperature, atmosphere, and charged Ba / Ti ratio.

When the heat treatment temperature (reaction temperature) is too low, the solid phase reaction between titanium oxide and barium oxide (partially barium carbonate) does not proceed sufficiently, and perovskite-type barium titanate tends not to be generated sufficiently. On the other hand, if the heat treatment temperature (reaction temperature) is too high, a different phase other than the perovskite structure such as Ba ₂ TiO ₄ is generated. In addition, it is possible to suppress the generation of a heterogeneous phase on the high temperature side by controlling the atmosphere, but the barium oxide completely changes to barium carbonate, and the shape of the barium compound at the time of crystallization changes the titanium oxide or formation. The perovskite-type barium titanate easily moves and aggregates, the barrier effect of excess Ba is weakened, necking particles are easily formed, the particle diameter is increased, and the target particle diameter cannot be obtained.

  In addition, the carbon remaining amount with respect to the calcining temperature plot differs depending on the atmosphere, and there is an effect of suppressing grain growth and suppressing the generation of a different phase that is not a perovskite phase.

  Other conditions in the heat treatment step (step S16) may be as follows, for example. Although there is no specific designation for the rate of temperature increase, for example, Δ300 ° C./hour, and the holding time at the heat treatment temperature is preferably 1 hour or more and 9 hours or less. The atmosphere may be air, water vapor, decarboxylated air, or a reduced pressure atmosphere.

  After the heat treatment, as shown in FIG. 4, heat-treated powder 18 in which barium titanate particles 19 are scattered in barium oxide particles (partially including barium carbonate) 20 is obtained.

  Next, barium oxide (partially barium carbonate) 20 is dissolved as the excess Ba of the heat-treated powder 18 after the heat treatment, and the barium titanate particles 19 are separated from the heat-treated powder 18 after the heat treatment (dissolution process: step S17). The separation method is not particularly limited, and may be a physical method or a chemical method. In this embodiment, a solution is added to the mixture after heat treatment to separate the barium titanate particles.

  Specifically, since barium oxide (partially barium carbonate) is easily dissolved in acid and barium titanate is difficult to dissolve in acid, by adding acid as a solution to the heat-treated powder 18 after heat treatment, Only the barium compound is dissolved, and the barium titanate particles 19 are obtained.

  In the dissolution step (step S17) in the present embodiment, acid is added dropwise to the heat-treated powder 18 suspended in ion-exchanged water and vigorously stirred while measuring the pH. At the stage where the excess barium is dissolved, even if the acid is added dropwise, the pH immediately becomes neutral, but when the excess barium is dissolved, the pH is saturated in the weak acid range of 4 to 5. The time point was defined as the end point of washing. It stirred for 24 hours in the stage where pH was saturated, and it confirmed that there was no change of pH. The stirring time is not particularly limited, but is preferably 3 hours or more and 24 hours or less.

  The acid used for dissolution is not particularly limited, but for example, hydrochloric acid, nitric acid, acetic acid, citric acid, tartaric acid, gluconic acid, malic acid, formic acid, hydrofluoric acid and the like are preferable. Among these, it is preferable to use acetic acid from the viewpoint of reusing Ba. In this embodiment, acetic acid is used.

  Due to the effect of the acid washing, it is possible to remove excess Ba compound that has prevented necking during calcination, and it is possible to obtain nanoparticles having a sharp particle size distribution.

  Control of dissolution of excess Ba is performed at pH, and acid is dropped while vigorously stirring the calcined powder slurry. The standard for the end of the washing step is the stage where the pH of the slurry is no longer changed from 5 to 5.5, and it is preferable to bring the pH to the strong acid side because it also dissolves Ba on the surface of the dielectric particles. Absent. Moreover, in order to perform melt | dissolution efficiently, acid washing | cleaning can also be performed, crushing with a ball mill.

  In this embodiment, barium oxide (partially barium carbonate) 20 is dissolved so that the Ba / Ti ratio of barium titanate does not become too small, but the specific surface area of heat-treated powder 18 and the conditions for acid dissolution are controlled. By doing so, the range of the Ba / Ti ratio can be adjusted.

The slurry obtained by washing as described above is subjected to solid-liquid separation by suction filtration (solid-liquid separation step: step S18), washed with water, and then dried at 130 ° C. for 2 hours to obtain the desired BaTiO ₃ powder 19. .

  As described above, a barium titanate powder that is an aggregate of barium titanate particles and a barium salt aqueous solution in which barium oxide (partially barium carbonate) is dissolved can be obtained. This solution can be reused as a starting barium source, as shown in FIG. Therefore, according to the manufacturing method of the barium titanate powder which concerns on this embodiment, barium titanate can be manufactured efficiently.

  Thus, according to the method for producing barium titanate powder according to the present embodiment, titanium / citric acid / barium slurry (gel) in which Ti stabilized by an acidic chelating agent and supersaturated Ba is dissolved is used. Further, the titanium / citric acid / barium slurry (gel) is uniformly dried and heat-treated, whereby barium titanate powder (dielectric particles) can be produced. By allowing Ba to exist excessively in the titanium / citric acid / barium slurry (gel), it is possible to suppress the grain growth of the target particles and obtain a nanoparticle-sized barium titanate powder having a good particle size distribution. Furthermore, since barium titanate powder is synthesized by solid-phase reaction, it is possible to produce barium titanate powder that has high crystallinity, high anisotropy, and no or very little intraparticle vacancies (defects). it can.

  That is, the barium titanate powder according to this embodiment can be obtained by using the method for producing a barium titanate powder according to this embodiment. In other words, in the solid-phase synthesis of barium titanate powder, while controlling the particle size, which has been regarded as a drawback until now, it has a good particle size distribution and enables nanoparticulate formation, which is an advantage of solid-phase synthesis. Barium titanate powder with no or very little pores (defects) in the particles can be produced.

<Ceramic electronic parts>
The barium titanate powder obtained as described above is suitably used as a dielectric material of a dielectric ceramic composition for forming a dielectric layer constituting a part of a ceramic electronic component. Referring to the drawings, an embodiment of a ceramic electronic component in which a dielectric ceramic composition obtained using a barium titanate powder obtained using the method for producing barium titanate according to this embodiment is applied as a dielectric layer However, it will be explained. In the present embodiment, a case where a multilayer ceramic capacitor is used as the ceramic electronic component will be described.

  FIG. 5 is a conceptual cross-sectional view schematically showing one embodiment of a ceramic capacitor. As shown in FIG. 5, the ceramic capacitor 30 includes a capacitor element body 31 and a pair of terminal electrodes (external electrodes) 32 formed at both ends of the capacitor element body 31. The capacitor element body 31 is formed in a rectangular parallelepiped shape having both side surfaces and four side surfaces including an upper surface, a lower surface, and both side surfaces. The size of the capacitor element body 31 is also not particularly limited, and is set to an appropriate size according to the application. In FIG. 5, the width direction of the capacitor element body 31 is X, and the thickness direction is Y.

  The capacitor element body 31 has a plurality of dielectric layers 33 and a plurality (for example, about 100 layers) of internal electrodes 34. The capacitor element body 31 is formed by alternately laminating a plurality of dielectric layers 33 and a plurality of internal electrodes 34. Capacitor element body 31 is formed by laminating a plurality of ceramic green sheets (unfired ceramic sheets), and laminating a laminated body containing a conductive paste of a predetermined pattern to be internal electrode 34 between the ceramic green sheets by thermocompression bonding. A rectangular parallelepiped sintered body obtained by cutting, degreasing and firing. The stacking direction of the dielectric layer 33 and the internal electrode 34 is the thickness direction Y of the capacitor element body 31. The capacitor element main body 31 is formed in a rectangular parallelepiped shape having both side surfaces and four side surfaces including an upper surface, a lower surface, and both side surfaces. For convenience of explanation, in FIG. 5, the number of laminated layers of the dielectric layers 33 and the internal electrodes 34 is set so as to be visible, but depending on the desired electrical characteristics, the number of laminated layers of the dielectric layers 33 and the internal electrodes 34 is set. The number may be changed as appropriate. The number of stacked layers may be, for example, several tens of the dielectric layers 33 and internal electrodes 34, or about 100 to 500 layers. Further, the actual capacitor element body 31 may be integrated to such an extent that the interlayer of the dielectric layer 33 cannot be visually recognized.

  The dielectric layer 33 is composed of a dielectric ceramic composition containing barium titanate manufactured by the method for manufacturing barium titanate according to the present embodiment. The dielectric layer 33 is obtained by firing a ceramic green sheet made of a dielectric ceramic composition. The dielectric ceramic composition is manufactured by the method for manufacturing barium titanate according to the present embodiment, has high crystallinity and anisotropy, has a particle size on the order of nanometers, and has a sharp particle size distribution. Lifetime and high dielectric constant. In addition, the dielectric ceramic composition may include a subcomponent. Subcomponents include oxides of Si, Mn, Cr, Ca, Ba, Mg, V, W, Ta, Nb and R (R is one or more of rare earth elements such as Y) and compounds that become oxides by firing Etc., and may contain one or more of these.

  One end of the internal electrode 34 is exposed from one of the end faces 36 a and 36 b of the capacitor element body 31, is connected to one external electrode 32, and the other end is insulated from the external electrode 32. The internal electrodes 34 respectively connected to the pair of opposed external electrodes 32 are alternately opposed to each other via the dielectric layer 33, and a plurality of layers are stacked with a predetermined interval.

  As a material constituting the internal electrode 34, any conductive material that is usually used as an internal electrode of a multilayer ceramic electronic component can be used. For example, Pd, Ag, Ni, alloys thereof, and the like are used as a main component. A material containing a conductive material is used.

  The external electrode 32 is provided so as to cover the end faces 36a and 36b of the capacitor element body 31 and a part of the upper surface 37a and the lower surface 37b. The external electrode 32 is connected to the internal electrode 34 at the end faces 36a and 36b of the capacitor element body 31 to constitute a capacitor circuit. The external electrode 32 can be used as long as it is a conductive material usually used as an external electrode of an electronic component. For example, at least one of Ni, Pd, Ag, Au, Cu, Pt, Sn, Rh, Ru, Ir, and the like can be used. Seeds or their alloys can be used. The external electrode 32 is formed by applying and baking a conductive paste containing a conductive material contained in the external electrode 32 on the end faces 36 a and 36 b of the capacitor element body 31. The external electrode 32 may be composed of a plurality of metal electrode layers. For example, a Ni plating layer and a Sn plating layer may be formed using a Cu plating layer as a base electrode.

  The ceramic capacitor 30 is manufactured as follows. First, the pre-firing dielectric layer and the pre-firing internal electrode layer are formed using the dielectric paste containing the barium titanate powder according to the present embodiment and the internal electrode layer paste. Subsequently, a green chip in which a dielectric layer before firing and an internal electrode layer before firing are laminated is manufactured, and a sintered body formed through a binder removal process, a firing process, and an annealing process performed as necessary. The multilayer ceramic capacitor 30 is manufactured by forming the external electrode 32 on the capacitor element body 31 configured.

  Since the multilayer ceramic capacitor 30 manufactured in this way is manufactured using the barium titanate powder according to the present embodiment, it has a higher temperature than that manufactured using a general barium titanate powder. Since it has a load life and a higher relative dielectric constant, a highly reliable electronic component can be provided.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  Hereinafter, the invention according to this embodiment will be described more specifically with reference to examples and comparative examples. However, the invention according to this embodiment is not limited to the following examples.

<Preparation of barium titanate powder>
[Sample Nos. 1 to 22]
A barium titanate powder was produced using the following raw material using the method for producing a barium titanate powder according to this embodiment as shown in FIG.
(Titanium aqueous solution)
A titanium chloride aqueous solution (trade name “titanium chloride aqueous solution”, manufactured by Wako Pure Chemical Industries, 16.5 wt% as Ti) was used.
(Chelating agent aqueous solution)
It was prepared by dissolving 740 g of citric acid monohydrate in 600 g of ion-exchanged water.
(Barium salt)
Barium acetate (trade name “Barium acetate”, manufactured by Tikamochi Pharmaceutical Co., Ltd.) was used.
(Titanium / chelating agent aqueous solution)
A titanium aqueous solution (750 g) was mixed with the chelating agent aqueous solution to prepare (5.9 wt% as Ti).

(Mixing barium salt powder into titanium / chelating agent aqueous solution)
Barium salt powder was mixed into the titanium / chelating agent aqueous solution. The mixing amount was set to 3 and 5 in terms of Ba / Ti molar ratio according to each example, and the mixing rate was 30 minutes for the total amount. Further, the barium salt powder was mixed by dissolving the titanium / chelating agent aqueous solution while stirring at a rotation speed of 350 rpm or more.

(PH adjustment of titanium / chelate / barium slurry)
The target pH of the titanium / chelate / barium slurry was set to 2, 3, and 4 according to each example. After adjusting the pH, the mixture was stirred for 3 hours to stabilize the titanium hydroxide gel.

(Spray dry drying)
The slurry was spray dried using a Büch B-290 spray dryer. The spray drying conditions were an inlet temperature of 220 ° C and an outlet temperature of 110 ° C to 130 ° C (uncontrolled). The feed rate of the raw material aqueous solution was adjusted while adjusting the gas supply rate and the liquid supply rate so that the spray cone was in a clean cone shape. The particle size of the dry powder was approximately 100 μm or less.

(Heat treatment (calcination))
The heat treatment was performed in an air atmosphere at a heat treatment temperature in the range of 650 ° C. to 750 ° C., a temperature increase rate of Δ300 ° C./hour, and a holding time of 1 hour to 9 hours.

(Cleaning of excess barium)
To dissolve the surplus barium, acetic acid was added dropwise while measuring the pH of the calcined powder suspended in ion-exchanged water so as to be 30 wt% and vigorously stirred. At the stage where the excess barium is dissolved, even if the acid is added dropwise, the pH immediately becomes neutral, but when the excess barium is dissolved, the pH is saturated in the weak acid range of 4 to 5. This was defined as the end point of washing. When the pH was saturated, the mixture was stirred for 3 hours, and after confirming that there was no change in pH, the mixture was stirred for 24 hours.

(Solid-liquid separation process)
The slurry after washing was separated into solid and liquid by suction filtration, washed with water, and dried at 130 ° C. for 2 hours to obtain the desired powder.

[Sample No. 23]
For sample No. 23, the Ba / Ti ratio was set to 2, and the subsequent steps were performed in the same manner as described above.

[Sample No. 24]
Sample No. 24 was obtained by setting the calcining temperature to 800 ° C., and the subsequent steps were performed in the same manner as described above.

[Sample No. 25]
Sample No. 25 had a calcining temperature of 450 ° C. and a calcining holding time of 18 hours, and the subsequent steps were performed in the same manner as described above.

[Sample No. 26]
Sample No. 26 was obtained by setting the calcining holding time to 18 hours, and the subsequent steps were performed in the same manner as described above.

[Sample No. 27]
Sample No. 27 was obtained by changing the calcining atmosphere to a carbon dioxide atmosphere, and the subsequent steps were performed in the same manner as described above.

[Sample No. 28]
In Sample No. 28, the pH was adjusted with hydrochloric acid to prepare an aqueous solution of titanium / barium / chelate instead of gel, and the subsequent steps were performed in the same manner as described above.

[Sample No. 29]
Sample No. 29 was a slurry in which barium acetate powder was mixed with acidic titania sol (manufactured by TDK), and the subsequent steps were performed in the same manner as described above.

[Sample No. 30]
Sample No. 30 was prepared by mixing barium carbonate powder and titanium dioxide powder having a BET specific surface area of 93 m ² / g so as to have a Ba / Ti ratio of 5, and wet-grinding to the same slurry concentration as in the examples. A slurry was prepared, and the subsequent steps were performed in the same manner as described above.

[Sample No. 31]
Sample No. 31 was prepared by adding a double amount of ion-exchanged water to the mixed slurry (gel) to prepare a slurry in which Ba was not saturated and dissolved, and the subsequent steps were performed in the same manner as described above.

[Sample No. 32]
Prepare barium carbonate with a BET specific surface area of 26 m ² / g and titanium oxide with a BET specific surface area of 50 m ² / g, adjust these so that Ba / Ti is 1.000, and wet mix with a ball mill for 24 hours. I did it. This was dried with a spray dryer and heat-treated at 1100 ° C. in the atmosphere. The obtained heat-treated powder was pulverized by a dry pulverizer to obtain Sample No. 32 powder.

[Sample No. 33]
Barium carbonate with a BET specific surface area of 26 m ² / g and titanium oxide with a BET specific surface area of 50 m ² / g are prepared, adjusted so that Ba / Ti is 1.050, and wet mixed with a ball mill for 48 hours. I did it. This was dried with a spray dryer and heat-treated at 850 ° C. in a vacuum atmosphere of 5 × 10 ² Pa to obtain a powder of Sample No. 33.

  Table 1 shows the Ba / Ti ratio, pH, and calcination conditions (calcination temperature, calcination holding time, atmosphere) of each sample.

<Evaluation>
Using the obtained barium titanate powder, the surface area and particle diameter of the barium titanate powder were measured by the BET surface area evaluation method (BET method). Moreover, X-ray diffraction measurement (X-Ray Diffraction: XRD) is performed, and X-ray diffraction intensity obtained by the measurement is analyzed by Rietveld method (Rietveld method, Rietveld method), c / a, ΔH (crystallinity) ), And the amount of barium carbonate was measured. Moreover, the barium titanate powder was observed by FE-SEM, the particle diameter of the barium titanate powder was measured, and the particle size distribution ((D90-D10) / D50) was evaluated. Further, the Ba / Ti ratio was measured by X-ray Fluorescence Analysis (XRF). Moreover, the pore of the barium titanate powder was observed using TEM.

  The measurement conditions of X-ray diffraction and particle size distribution are as shown below.

(X-ray diffraction)
In X-ray diffraction, Cu-Kα ray was used as an X-ray source. The measurement conditions were a voltage of 45 kV and a current of 40 mA, and a range of 2θ = 20 ° to 130 ° with a scanning speed of 0.08 deg / sec.

  The full width at half maximum (ΔH) of the (111) peak obtained by X-ray diffraction was evaluated. In this example, in consideration of the particle size, crystallinity, and anisotropy, c / a is preferably 1.0045 or more, the full width at half maximum (ΔH) is 0.310 or less, and the amount of barium carbonate is 3.2 mass% or less was made favorable.

(Particle size distribution)
FE-SEM observation was performed about the primary particle which comprises the obtained powder, 500 particles were observed, and the particle diameter was measured. The particle diameter at which the cumulative number was 10% was D10, the particle diameter at which the cumulative number was 50% was D50, and the particle diameter at which the cumulative number was 90% was D90. From the obtained D10, D50 and D90, (D90−D10) / D50 was calculated. In this example, (D90-D10) / D50 was determined to be 2.0 or less.

  The test results are shown in Tables 1 and 2.

  FIG. 6 is a diagram showing an XRD result of the mixture after the heat treatment. FIG. 7 is a diagram showing an XRD result of a sample obtained by removing excess barium from the heat-treated mixture. As shown in FIG. 6, it was confirmed that the mixture after the heat treatment produced various barium salts and barium titanate. Further, as shown in FIG. 7, the barium titanate powder obtained by dissolving the heat-treated mixture contains almost no foreign phase, and excess barium is removed from the heat-treated mixture. It could be confirmed.

  FIG. 8 is an SEM photograph of the mixture after the heat treatment. FIG. 9 is an SEM photograph of a sample from which excess barium has been removed from the mixture after heat treatment, and FIG. 10 is another SEM photograph of a sample from which excess barium has been removed from the mixture after heat treatment. As shown in FIG. 8, the heat-treated mixture can be confirmed to contain barium titanate powder, but is not dispersed individually. On the other hand, when excess barium is removed from the mixture, as shown in FIGS. 9 and 10, the barium titanate powder produced by the method according to the present invention is a square crystal and has good crystallinity. It was visually confirmed that there was little variation in diameter.

  Moreover, the TEM photograph of the barium titanate powder of the sample number 5 is shown in FIG. As shown in FIG. 11, it was confirmed that the barium titanate powder produced by the method according to the present invention has no intraparticle pores.

  From the sample numbers 1 to 8, it can be seen that the calcining holding temperature and the calcining holding time are effective in controlling the particle diameter according to the method for producing the barium titanate powder according to the present embodiment. It can be seen that when the calcining holding time is short and the calcining holding temperature is low, the particle diameter is reduced, but the crystallinity and anisotropy are also deteriorated.

  From the sample numbers 1 to 16, it can be seen that the Ba / Ti ratio is effective in controlling the particle diameter of the barium titanate powder obtained by the method for producing a barium titanate powder according to this embodiment. It can be seen that when the charged Ba / Ti ratio is large, the particle diameter of the barium titanate powder can be reduced and the crystallinity and anisotropy are increased even if the calcining holding temperature is increased.

  From sample numbers 11-13 and sample numbers 17-22, it can be seen that the particle size can be controlled by the pH of the gel slurry. It can be seen that when the pH is high, the particle diameter of the produced barium titanate is small, and when the pH is low, the particle diameter is large.

  From Table 2, as shown in sample number 23, when the Ba / Ti ratio is 2, the amount of Ba in the titanium gel is small, and a large number of titanium oxide particles 16 are scattered in the barium salt particles 15 as shown in FIG. The (dispersed) dry powder (mixture) 17 could not be obtained, and the periphery of the titanium oxide particles 16 was not covered with the barium salt. Therefore, the BET specific surface area is small, and the target particle size is not produced.

  From Table 2, as shown in Sample No. 24, when the calcining temperature was 800 ° C. or higher, the particle diameter of the obtained barium titanate particles was large and did not fall within the predetermined target particle diameter range. This is because barium carbonate conversion of the Ba salt has progressed, and as a result, the density of the Ba salt has changed and the crystallization has caused aggregation of the titanium oxide during calcining and the generated barium titanate to progress grain growth.

  FIG. 12 is a diagram showing an XRD chart of sample number 25. As shown in FIG. 12, when the calcining temperature was set to 450 ° C. or lower, barium titanate was not generated.

  From Table 2, when the calcining holding time was 18 hours as in Sample No. 26, the obtained barium titanate particles were necked and the particle size distribution was deteriorated. This can be said that the barium carbonate conversion of the Ba salt proceeds, and as a result, the titanium oxide aggregates due to the change in density and crystallization of the Ba salt.

  Moreover, the photograph of FE-SEM of the sample number 26 is shown in FIG. As shown in FIG. 13, the barium titanate powder produced with a calcining holding time of 18 hours had poor crystallinity, large particle size variation, and it was confirmed visually that titanium oxide was aggregated. It was.

  From Table 2, when the calcining atmosphere was changed to a carbon dioxide atmosphere as in Sample No. 27, the Ba salt did not progress to barium oxide, and became completely barium carbonate. As a result, the spherical barium salt after spray drying was transformed into acicular barium carbonate, and titanium oxide aggregated during the transformation. As a result, the obtained barium titanate particles grew at a stretch, and the intended particle size distribution and particle size were not achieved.

  From Table 2, as shown in Sample No. 28, when the drying process was performed in the state of an aqueous solution without passing through the gel process, the titanium raw material aggregated. This can be said to be because barium and titanium are separated and dried during drying because a hydrogen bond network of the titanium raw material is not formed.

  From Table 2, as in sample number 29, in the method of sample number 29, when the barium acetate powder was mixed with the titania sol, the titania particles were aggregated. Further, since titanium oxide was used as a starting material, the reactivity at low temperature was low.

  From Table 2, when the raw material was prepared by the method of Sample No. 30, in the calcining temperature range as low as 800 ° C. or less, barium titanate particles were not completely generated, and unreacted titanium oxide remained. This is because Ba and Ti raw materials are in contact with each other by calcination in powder mixing, and the barium titanate particles are in contact with titanium oxide on the surface as in the method for producing a barium titanate powder according to this embodiment. Not. Therefore, it does not react completely unless it is raised to a temperature at which the raw material undergoes a diffusion reaction. Therefore, it seems that barium titanate was not completely formed.

  From Table 2, when the raw material was prepared by the method of sample number 31, it became barium titanate having a large particle size. It can be said that this is because the titanium concentration decreases and does not gel, or the Ba concentration decreases and the Ba barrier between Ti in the dry powder becomes thin, and the thickness of the Ba salt on the dry powder surface increases.

  From Table 2, when the raw material was prepared by the method of sample number 32, the particle size distribution deteriorated. This is that the charge amount of Ba / Ti is 1. It is considered that strong necking particles are formed by the high heat treatment temperature, and this is because the BET specific surface area is adjusted by dry pulverization. Further, when the raw material was prepared by the method of Sample No. 33 and subjected to heat treatment, the particle size distribution was poor and the anisotropy was also lowered. This is presumably because the amount of Ba / Ti charged is 1.05, and thus there is no effect of the Ba wall obtained in the present invention.

11 Water 12 Barium ion 13 Titanium compound 14 Citric acid 15 Barium salt particles 16 Titanium oxide particles 17 Dried powder (mixture)
18 Heat-treated powder 19 Barium titanate (BaTiO ₃ ) particles 20 Barium oxide (partially barium carbonate)
30 Ceramic capacitor 31 Capacitor element body 32 Terminal electrode (external electrode)
33 Dielectric layer 34 Internal electrodes 36a, 36b End surface 37a Upper surface 37b Lower surface

Claims (10)

Using a titanium aqueous solution and barium salt powder as starting materials, the starting material is mixed and gelled,
A drying step of drying the gelled mixture;
A heat treatment step of heat-treating the dry powder to produce barium titanate particles;
A separation step of separating the barium titanate particles from the heat-treated powder,
A method for producing a barium titanate powder characterized by comprising:   The method for producing barium titanate powder according to claim 1, wherein the titanium aqueous solution is a mixed aqueous solution of a water-soluble titanium raw material and an acidic chelating agent.   The method for producing a barium titanate powder according to claim 1 or 2, wherein the barium salt powder is mixed three times or more in molar ratio with respect to the titanium raw material.   The method for producing a barium titanate powder according to claim 2, wherein the mixed aqueous solution is a saturated aqueous solution in which barium salt powder has reached saturation solubility.   The dried powder that has undergone the drying step has barium salt particles as main particles, in which one or more titanium oxides are dispersed without being in contact with each other. The manufacturing method of the barium titanate powder as described in any one of these.   The method for producing barium titanate powder according to any one of claims 1 to 5, wherein the heat treatment step turns the barium salt into a basic barium compound.   The method for producing barium titanate powder according to any one of claims 1 to 6, wherein a heat treatment temperature in the heat treatment step is 500 ° C or higher and lower than 800 ° C.   In the separation step, the heat-treated powder and solvent are mixed to dissolve the excess basic barium salt, which is an unreacted barium compound, and the barium titanate particles are separated from the heat-treated powder after the heat treatment. It has a process, The manufacturing method of the barium titanate powder as described in any one of Claim 1 to 7 characterized by the above-mentioned. The barium titanate powder produced by the method for producing a barium titanate powder according to claim 1 is a barium titanate powder that is an aggregate of barium titanate particles having a perovskite crystal structure,
C / a indicating the ratio of the c-axis lattice constant to the a-axis lattice constant in the perovskite crystal structure is 1.0045 or more in the perovskite crystal structure, and is observed by X-ray diffraction. The half-width of the (111) peak is 0.25 or less, the specific surface area by the BET method is 3.3 m ² / g or more and 25 m ² / g or less, and the particle diameter at which the cumulative number becomes 10% is D10. Barium titanate powder, wherein (D90-D10) / D50 is 2.0 or less, where D50 is the particle diameter at which the number is 50% and D90 is the particle diameter at which the cumulative number is 90% . A method of manufacturing an electronic component having a dielectric layer and an electrode layer,
A pre-firing dielectric layer forming step of forming a pre-firing dielectric layer comprising the barium titanate powder according to claim 9;
A firing step of firing the pre-fired dielectric layer;
A method for manufacturing an electronic component, comprising: