JP2767584B2 - Method for producing fine perovskite ceramic powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is to produce a perovskite-type ceramic fine powder by a so-called wet method for forming a precipitate from an oxalic acid solution containing Ti and an acetic acid solution containing another metal element. About the method. [Prior Art] Perobusukato ceramics are generally expressed as ABO _3, the powder ferroelectric is used as a raw material for an electrical member such as a piezoelectric element. For example, Pb (Zr, Ti) O ₃ -based perovskite solid solution ceramics are known to have particularly high piezoelectric properties. However, in order to further improve the dielectric constant and the piezoelectric properties, certain metal elements such as Sr, B
In many cases, one or more of a, Nb, Ta, Mg, Fe, Mn, Co, and Ni are added and used. Many methods for producing these perovskite-type ceramic powders have been developed, including a dry method, a wet method, and a combination of both methods. For example, recently, an oxalic acid ethanol method (Kamakyogyo, 94 [5], p. 1823, 1986), An improved method (JP-A-61-251519) has been proposed. These conventional methods were developed focusing on the fact that oxalic acid is soluble in ethanol and isopropanol and that the oxalates of Pb, Zr, and Ti are hardly soluble in alcohol. Specifically, an oxalic acid alcohol solution obtained by dissolving oxalic acid in alcohol and a nitric acid solution in which Pb, Zr, and Ti ions are dissolved are mixed to form a precipitate composed of a complex oxalate. After washing the obtained precipitate with alcohol, excess, dried and pulverized in air, 500-110
This is a method for producing perovskite ceramic powder that is calcined (pyrolyzed) at 0 ° C. [Problems to be Solved by the Invention] In the conventional method, the complex oxalate is formed and precipitated in a solution containing a nitrate group, so that the nitrate group is adsorbed on the surface of the composite oxalate particles. Since the formed complex oxalate has a very high surface activity, the adsorbed nitrate cannot be sufficiently removed by washing with water or alcohol. Therefore, the composite oxalate is dried while adsorbing nitrate and calcined in a calciner. Therefore, at the temperature of calcination, nitrate radicals are decomposed and gasified as nitrogen oxides, which erode the furnace wall and reduce its durability, and the nitrogen oxide gas discharged from the furnace reduces the environment. There were some operational problems such as worsening. [Means for Solving the Problems] The present inventors have studied the wet method capable of forming a composite oxalate precipitate using a compound containing no nitrogen, and as a result, have completed the invention described below. That is, one of the present invention is a compound represented by the general formula ABO ₃ (where A is one or more kinds of oxygen 12 coordination metal elements, B is two or more kinds of metal elements, one is Ti, and the other is Ti.
One or more selected from oxygen six-coordinate metal elements other than Ti are shown. A solution obtained by dissolving a titanium alkoxide in an alcoholic oxalate solution (hereinafter referred to as "solution (I)") in the production of the perovskite-type ceramic fine powder represented by
And an acetic acid aqueous solution (hereinafter, referred to as "solution (II)") containing a component A and a metal component B other than Ti to form a precipitate, which is dried and calcined to form a perovskite. Another aspect of the present invention is a method for producing a perovskite-type ceramic fine powder produced by adding a powder of Nb ₂ O ₅ and / or Ta ₂ O ₅ in the production process. It is. Here, the perovskite-type ceramics represented by the general formula ABO ₃ has a structure in which B atoms occupy the center of a cubic lattice and are octahedrally surrounded by six O ions, and A atoms are located in the center of the cubic lattice. It is a ceramic on which a perovskite structure is formed. Therefore, the B atom has six O
The atoms, A atoms, are surrounded by 12 O atoms, and the AO atoms form a cubic close-packed lattice. The oxygen 12-coordinating metal element of A includes Pb, Sr, La, Ba,
There are Ca and the like. As the oxygen 6-coordinate metal element of B, Ti,
Zr, Mg, Fe and the like can be mentioned. Hereinafter, the present invention will be described in detail from the first invention. The raw materials used in the first invention are oxalic acid, alcohol, titanium alkoxide, a compound containing the A component, and B containing no Ti.
Component compounds as well as acetic acid or acetate. As oxalic acid, alcohol and titanium alkoxide, those commercially available are usually used. The alcohol is not particularly limited, such as ethanol, methanol, n-propanol, iso-propanol, and n-butanol, but preferably contains 30 vol% or more of alcohol and 10 vol% or more of water. Considering economy, methanol is cheap and desirable. As oxalic acid, either anhydride or dihydrate may be used. The titanium alkoxide is preferably titanium tetraisopropoxide, but is not particularly limited as long as the alkoxide is soluble in an oxalic acid alcohol solution. The compound containing the component A and the compound containing the component B other than Ti do not contain nitrogen such as acetate, carbonate, and hydroxide,
Further, those that dissolve in acetic acid are used. Next, a method for preparing the solution (I) using oxalic acid, alcohol, and titanium alkoxide will be described. The method of dissolving oxalic acid in alcohol and the method of dissolving titanium alkoxide in the obtained alcoholic oxalic acid solution to prepare the solution (I) are both carried out by conventional methods. The amount of oxalic acid used varies depending on the type and amount of the compound used, but is not particularly limited as long as it is at least the amount necessary for precipitation as a complex oxalate. The amount of the alcohol used may be an amount sufficient to completely dissolve oxalic acid. The solution (II) is prepared from each compound containing the component A and the component B other than Ti by dissolving the compound in water if the compound is an acetate, and in the case of a carbonate or a hydroxide. Dissolve in acetic acid aqueous solution. The dissolution is performed by a conventional method. The dissolution amount of each compound of the component A and the component B other than Ti and the mixing amount of the solutions (I) and (II) in forming the solution (II) are determined by the amount of the metal element contained in the perovskite fine powder finally obtained. Must be dissolved to have a desired composition ratio, but the composition ratio is not particularly limited in the present invention. The mixing of the solutions (I) and (II) can be performed by simply adding one solution while stirring the other solution, whereby oxalates containing the respective metal elements are formed and mixed as a composite oxalate. Co-precipitate in a wet state The resulting precipitate is dried after drying in the air.
By calcining at 1100 ° C., preferably 500-900 ° C., a fine powder of perovskite ceramics having a submicron particle size can be obtained. A second invention of the present invention is a method for producing a multi-component perovskite ceramic fine powder by adding a powder of Nb ₂ O ₅ and / or Ta ₂ O ₅ in the production process of the first invention. Nb ₂ O ₅ and Ta ₂ O ₅ are both commercially available. These compounds may be added at any step before the calcination step of the first invention. For example, the production process of either solution (I) or solution (II), solution (I) and solution (II)
May be added at any stage, such as in the process of mixing, in the suspension after mixing, or in the dried product of the precipitate. The same effect can be obtained by adding Nb ₂ O ₅ and / or Ta ₂ O ₅ powder in two parts and adding them at appropriate stages. It is preferable that the addition be performed as early as possible because mixing becomes sufficient. Only one of Nb ₂ O ₅ and Ta ₂ O ₅ may be added, or both compounds may be added. The addition amount is not particularly limited in the present invention. The fineness of Nb ₂ O ₅ and Ta ₂ O ₅ is preferably as fine as possible for uniform dispersion. In particular, when it is added to a suspension, it is desirable that the average particle size is 3 μm or less since sedimentation and separation from a precipitate do not occur. Hereinafter, the present invention will be described with reference to examples. Example 1 Pb (Ti, Zr) O ₃ was produced as follows. Oxalic acid (dihydrate) 140 g (1.1 mol) was added to methanol (9
9vol%) 72.2m of titanium tetraisopropoxide (Ti concentration 3.323 mol /) was added to the solution dissolved in 1 while stirring.
l was added as a mist to produce a clear solution (I). On the other hand, 300 ml of pure water was added to zirconyl acetate (Zr concentration, 1.458 mol /), and then, with stirring, 189.7 g of lead acetate (trihydrate) (0.5 mol in terms of PbO) was added to dissolve the transparent solution (II). Was made. The solution (II) was atomized while stirring the solution (I) to form a precipitate, and the precipitate was separated by suction (paper 5C). After drying this precipitate at 70 ° C for 24 hours,
Calcination was performed in an electric furnace at 600 ° C. for 1 hour. When the fineness of the fine powder and the resulting mineral were examined by an automatic sedimentation type particle size analyzer and an X-ray diffractometer, it was a single mineral perovskite-type ceramic fine powder having an average particle diameter of 0.3 μm. Example 2 A perovskite-type ceramic fine powder composed of (Pb, La) (Ti, Zr, Mg) O ₃ was produced as follows. 126.0 g of oxalic acid dihydrate in methanol (99.9 vol%) 300
While stirring the solution dissolved in 5 ml, 52.7 ml of titanium tetraisopropoxide (Ti concentration 3.323 mol /) was added in the form of a mist, and 500 ml of pure water was further added to obtain a transparent solution (I).
Was made. On the other hand, the solution (II) was prepared as follows. That is, pure water was added to 222.9 ml of zirconyl acetate (Zr concentration 1.458 mol /).
400 ml was added, and a clear solution in which 174.5 g (0.46 mol in terms of PbO) of lead acetate trihydrate was dissolved with stirring, and 50 ml of pure water was added to 50 ml of acetic acid, and 6.5 g of La ₂ O ₃ powder and MgCO ₃ were stirred. Powder 1.
A transparent solution (II) was prepared by mixing 7 g (0.8 g in terms of MgO) of a solution dissolved therein. Next, while stirring the solution (I), the solution (II) was atomized to form a precipitate, and the precipitate was separated by suction. After drying the obtained precipitate at 70 ° C for 24 hours,
Calcination was performed in an electric furnace at 0 ° C. for 2 hours. The obtained calcined product was examined for fineness and generated minerals. As a result, it was a fine powder composed of a single phase of a tetragonal perovskite oxide having an average particle size of 0.5 μm. Example 3 A (Pb, Sr) (Ti, Zr) O ₃ —Nb ₂ O ₅ perovskite solid solution was produced as follows. While stirring, a solution of 113.4 g (0.9 mol) of oxalic acid (dihydrate) in methanol (containing 10 vol% of water) was mixed with titanium tetraisopropoxide (Ti concentration 3.328).
70.7 ml of mol /) were nebulized and a clear solution (I) was prepared. On the other hand, 180.17 g of lead acetate (trihydrate) in 500 ml of ion-exchanged water
(0.475 mol in terms of PbO) and 5.37 g (0.025 mol in terms of SrO) of strontium acetate (1/2 water salt) were dissolved with stirring, and further an aqueous zirconyl acetate solution (Zr concentration: 1.458 mol /
) 181.7 ml was added to make solution (II). While stirring the solution (I), the solution (II) was atomized to form a precipitate, and 1.7 g of niobium pentoxide powder having an average particle size of 0.8 μm was further suspended. The mixture was sufficiently stirred for about one hour.
The precipitate was separated by suction (paper 5C). This precipitate
After drying at 70 ° C. for 24 hours, it was calcined in an electric furnace at 600 ° C. for 1 hour in the atmosphere. When the fineness of this fine powder and the minerals formed were examined by an automatic sedimentation type particle size analyzer and an X-ray diffractometer, the average particle size was 0.3 μm, the X-ray profile was a tetragonal phase perovskite type, and SrCO ₃ and SrO ₃ were used. , Nb ₂ O _{5 and the} like were not present. [Effect of the Invention] Since the present invention does not use nitrate used in the conventional method at all, there is no need to wash the precipitate, there is no generation of nitrogen oxides in the calcination step, furnace maintenance and environmental Various problems have been solved, and it has become possible to add elements that are difficult to become solutions, such as Ta and Nb, which were impossible with the conventional method.
It can be applied to the production of many kinds of perovskite type ceramic fine powder.

Claims (1)

(57) [Claims] General formula ABO ₃ (where A is one or more of oxygen 12 coordination metal elements, B is two or more metal elements, one is Ti, the other is
One or more selected from oxygen six-coordinate metal elements other than Ti are shown. In the production of perovskite-type ceramic fine powder represented by), a solution in which a titanium alkoxide is dissolved in an oxalic acid alcohol solution and an aqueous acetic acid solution containing a metal element of component A and component B other than Ti are mixed to form a precipitate. A method for producing perovskite-type ceramic fine powder, comprising drying the precipitate and calcining the precipitate. 2. The method for producing a bevelskite-type ceramic fine powder according to claim (1), wherein the powdery Nb ₂ O
_{5. A} method for producing perovskite-type ceramic fine powder, characterized by adding ₅ and / or Ta ₂ O ₅ .