JPH0457614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing raw material powders of perovskites and solid solutions thereof.

Perovskites and their solid solutions are piezoelectric materials,
Ceramics are widely used for functionality such as dielectrics, semiconductors, sensors, and optoelectronic materials. Recently, there has been a desire to further improve this functionality, and raw material powders of perovskite and its solid solution that are easy to sinter, have uniformity, have high bulk density, and are low cost are available in large quantities to meet this demand. There is a need for the development of technology that allows for efficient manufacturing.

(Prior Art and its Problems) Dry methods, coprecipitation methods, and multi-stage wet methods are conventionally known as methods for producing perovskite raw material powders.

The dry method is a method in which compounds of constituent raw materials are mixed in a dry method and then calcined. However, with this method, it is difficult to obtain a raw material powder with a uniform composition, so it is difficult to obtain a perovskite with excellent functionality, and the sinterability is also not sufficient.

The coprecipitation method is a method in which a mixed solution is prepared by combining all of the constituent components, a precipitate-forming liquid such as an alkali is added to the mixed solution to cause coprecipitation, and the coprecipitate is dried and calcined.

According to this coprecipitation method, it is easy to obtain a powder with excellent uniformity, but because of its uniformity, the particles coagulate to form secondary particles during precipitate formation, drying, or calcination, and are susceptible to sintering. It had some serious flaws.

In addition, in the coprecipitation method, if the precipitate forming ability of each component in the precipitate forming solution is not the same, for example, one component will form substantially 100% of the precipitate, while another component will only partially form a precipitate. Therefore, it was difficult to obtain a product with a desired composition.

The multi-stage wet method is disclosed in JP-A No. 61-53113 and JP-A-Sho.
As described in Publication No. 61-53115, etc., the above-mentioned drawbacks of the coprecipitation method are solved by precipitating each component in stages. However, even in the multi-stage wet method, it was difficult to precipitate substantially 100% of the Mg component, Zn component, Ni component, and Co component.

(Objective of the Invention) An object of the present invention is to provide a method that improves the multi-stage wet method and can completely precipitate all the components to produce a raw material powder of perovskite and its solid solution having a desired composition. be.

Another object of the present invention is to provide a method for efficiently producing raw material powder of perovskite and its solid solution that satisfies the four requirements of easy sinterability, uniformity, low cost, and high bulk density. be.

(Technical Means for Solving the Problems) The present inventors have conducted intensive research to achieve the above object, and as a result, have arrived at the present invention.

The present invention _is based on _{the general formula} :
(PbZrO ₃ ) (where A represents at least one of Mg, Zn, Ni, and Co; B represents at least one of Nb and Ta; x, y, and z represent mol%; x
+y+z=100. ) When producing the raw material powder of perovskite and its solid solution,
After contacting each component solution of B, Pb, Ti, and Zr with a precipitate-forming solution to generate precipitates of each component in a stepwise manner, the concentration of ions generated from the precipitate-forming agent in the precipitate-containing solution was 0.2. The precipitate is washed so that the concentration is mol/l or less, and then the pH of the precipitate-containing liquid is adjusted to 11.5 or higher with a precipitate-forming solution, and then a solution of the hydroxide of component A is added to remove the precipitate containing component A. The present invention relates to a method for producing an easily sinterable composite perovskite raw material powder, which comprises forming and calcining the obtained precipitate.

In the present invention, the term "solution" refers to a solution in which soluble substances are dissolved or a suspension in which insoluble substances are dispersed.

General formula in the present invention X[Pb(A _1/3 B _2/3 )O ₃ ]-y(PbTiO ₃ )-z
The A component of perovskite and its solid solution represented by (PbZrO ₃ ) is at least one of Mg, Zn, Ni, and Co, the B component is at least one of Nb and Ta, and Pb(A _1/3 B _{2/ 3} ) Pb in O ₃ and (A _1/3
B _2/3 ) component atomic ratio [Pb/(A _1/3 B _2/3 )],
Atomic ratio of Pb and Ti in PbTiO ₃ (Pb/Ti) and atomic ratio of Pb and Zr in PbZrO ₃ (Pb/Zr)
is usually 1.0, but nonstoichiometric perovskites in which this atomic ratio is shifted to a value higher or lower than 1.0 are also included.

In addition, x, y and z in the above general formula represent mol% and can take various values depending on the use, but usually x is 5 to 90, y is 5 to 80, and z is 5 to 80 mol%.
It is preferable to select from the range of . If it is outside this range, it is not preferable because it will cause problems in terms of characteristics.

A compound containing a metal element of B component, which is a component of perovskite and its solid solution, and a Pb component,
Component compounds for preparing a solution of Ti component and Zr component compounds include, but are not particularly limited to, their hydroxides, carbonates, oxysalts, sulfates, nitrates, inorganic salts such as chlorides, and acetic acid. Salts, organic acid salts such as oxalates, oxides, etc. are selected as appropriate.
Alkoxides can also be used as the titanium component. Further, as the compound containing a metal element as component A, hydroxides thereof are used. These are generally used as an aqueous solution, but if they are not soluble in water, they can be made soluble by adding an acid, and insoluble raw materials may be used as a suspension solution. Also, an alcohol solution may be used instead of an aqueous solution.

Examples of the precipitate-forming liquid include solutions of ammonia, ammonium carbonate, caustic alkali, amine, oxalic acid, alkylamine, and the like. Examples of alkylamines include primary amines having a lower alkyl group such as methylamine, ethylamine, propylamine, and butylamine, primary amines having a lower alkyl group such as cyclohexylamine, secondary amines having a lower alkyl group such as dimethylamine and diethylamine, and triethylamine. Mention may be made of tertiary amines having lower alkyl groups such as

When bringing a solution of each component of B, Pb, Ti, and Zr into contact with a precipitate-forming solution to form a precipitate of each component in a stepwise manner, care must be taken to prevent the Pb component and Ti component from forming precipitates at the same time. In addition, it is preferable to prevent the formation of lead chloride precipitates. The specific method is as follows: (1) From a solution of a compound containing the metal element of component B and a solution of compounds of Pb and Zr, a precipitate forming solution is used to separate the components B, Pb, and Zr. A method of forming a precipitate and then adding a solution of a Ti compound to form a precipitate of a Ti component, or (2) a method of forming a solution of a compound containing a metal element as component B, a solution of a Zr compound, and a Ti compound. From the solution, use the precipitate forming solution to remove component B, Zr.
component and Ti component, then Pb
Preferred examples include a method in which a solution of the compound is added to form a precipitate of the Pb component.

In the method (1) or (2) above, the B component, Pb
In order to form a precipitate of the component and Zr component, or a precipitate of the B component, Zr component and Ti component, each component solution may be added to the precipitate forming liquid while stirring the precipitate forming liquid. On the contrary, it may be added. In addition, each component solution can be prepared in multiple stages as necessary.
Alternatively, they may be brought into contact with the precipitate forming solution alternately.
It is preferable that the addition be carried out while sufficiently stirring the liquid.

The precipitate obtained by the above method is washed with water or the like by a normal washing method such as a decantation method to reduce the concentration of ions generated from the precipitate forming agent in the precipitate-containing liquid.
Adjust so that it is 0.2 mol/l or less. By controlling the concentration of ions generated from the precipitant to 0.2 mol/l or less, undesirable impurities such as Cl ^- and NO ₃ ^- ions in the solution can be removed.

Next, the pH of the precipitate-containing solution is adjusted to 11.5 or higher, preferably 12.0 to 12.5, using a precipitate-forming solution, and a solution of the hydroxide of component A is added to form a precipitate containing component A.

The precipitate obtained by the above method can be filtered, dried, and then calcined without any washing. According to this method, it is possible to prevent the elution of the precipitate of component A due to washing, which has been a problem in the past, and it is possible to obtain a raw material powder of perovskite and its solid solution having a desired composition. The precipitate may be dried under atmospheric pressure or under reduced pressure.

If the calcination temperature is too low, the dehydration and thermal decomposition of the precipitate will be insufficient, and if it is too high, the powder will become coarse.
A range of 1200°C is preferred.

(Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 37.5[Pb(Mg1 _{/ 3Nb2/ 3} )O3]-37.5( _PbTiO3 )-
25.0 (PbZrO ₃ ) 13.509 g of niobium pentachloride (NbCl ₅ ) in ethanol
Dissolve in 300ml and add 6N ammonia aqueous solution.
Added 1000ml. This is followed by lead nitrate [Pb(NO ₃ ) ₂ ]
A solution of 66.242g dissolved in 500ml water was added.
Additionally, 16.11g of zirconyl chloride (ZrOCl _{2.8H 2} O)
A solution of 500 ml of water was added to form a precipitate. Next, add 14.23g of titanium tetrachloride (TiCl ₄ ) to water.
A solution dissolved in 500 ml was added to form a precipitate.
After washing the precipitate by repeatedly decanting it with water four times and adjusting the ammonium ion concentration to 0.11 mol/l,
50 ml of an aqueous solution containing 10 ml of 15N ammonia water was added to adjust the pH to 12.1. A solution of 5.141 g of magnesium hydroxide [Mg(OH) ₂ ] dispersed in 350 ml of water was gradually added to this solution to form a precipitate. This precipitate was separated and dried without washing, and the composition was analyzed, and the elemental composition was found to be the same as that of the initial precipitate.
Further, this precipitate was calcined at 750°C for 2 hours. Ethanol was added to this powder and it was ball milled, and part of the powder was observed using a transmission electron microscope, and the particle size was uniform at about 0.2 μm.

Add 0.8wt% polyvinyl alcohol to this calcined powder.
It was added, molded at 1 t/cm ² , and sintered at 1150° C. for 2 hours in a lead atmosphere. The density of the obtained sintered body is
It was 7.99g/ ^cm2 .

Example 2 12.5 [Pb (Zn _1/3 Nb _2/3 ) O ₃ ] −50.0 (PbTiO ₃ ) −
37.5 (PbZrO ₃ ) 4.503 g of niobium pentachloride (NbCl ₅ ) in ethanol
Dissolve in 100ml and add 6N ammonia aqueous solution.
Added 1000ml. This is followed by lead nitrate [Pb(NO ₃ ) ₂ ]
A solution of 66.242g dissolved in 500ml water was added.
Additionally, 24.17g of zirconyl chloride (ZrOCl _{2.8H 2} O)
A solution of 500 ml of water was added to form a precipitate. Next, add 18.97g of titanium tetrachloride (TiCl ₄ ) to water.
A solution dissolved in 500 ml was added to form a precipitate.
After washing the precipitate by repeatedly decanting it with water four times and adjusting the ammonium ion concentration to 0.11 mol/l,
50 ml of an aqueous solution containing 10 ml of 15N ammonia water was added to adjust the pH to 12.1. Add zinc hydroxide [Zn
A solution of 2.92 g of (OH) ₂ ] dispersed in 350 ml of water was gradually added to form a precipitate. This precipitate was separated and dried without washing, and the composition was analyzed, and the elemental composition was found to be the same as that of the initial precipitate. Further, this precipitate was calcined at 750°C for 2 hours. Ethanol was added to this powder and it was ball-milled, and part of the powder was observed using a transmission electron microscope, and the particle size was found to be uniform at about 0.3 μm.

Add 0.8wt% polyvinyl alcohol to this calcined powder.
It was added, molded at 1 t/cm ² , and sintered at 1150° C. for 2 hours in a lead atmosphere. The density of the obtained sintered body is
It was 7.85g/ ^cm3 .

Comparative example 1 37.5 [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] −37.5 (PbTiO ₃ ) −
25.0 (PbZrO ₃ ) Niobium oxide (Nb ₂ O ₅ ) 33.3g, lead oxide (PbO)
223.2g, titanium oxide (TiO ₂ ) 30.0g, zirconium oxide (ZrO ₂ ) 30.8g, and magnesium oxide (MgO) 5.1g were weighed, a small amount of water was added to them, they were thoroughly mixed by stirring, and then dried. did. this
It was calcined at 750°C for 2 hours. The composition ratio of the obtained calcined powder was the same as in Example 1, but the TEM of the particles
In the photograph, the particle size was 1 to 2 μm and nonuniform. When this calcined powder was fired in the same manner as in Example 1, the density of the sintered body was 7.30 g/cm ³ .

Comparative Example 2 In Example 1, magnesium acetate (MgO) with a particle size of 1 to 3 μm was used instead of magnesium hydroxide.
A calcined powder was obtained in the same manner as in Example 1 except that 3.55 g was used. The particle size was several μm and nonuniform. When this calcined powder was fired in the same manner as in Example 1, the density of the sintered body was 7.50 g/cm ³ .

(Effect of the invention) X[Pb(A _1/3 B _2/3 )O ₃ ]−y(PbTiO ₃ )−z
(PbZrO ₃ ) (where A represents at least one of Mg, Zn, Ni, and Co; B represents at least one of Nb and Ta; x, y, and z represent mol%; x
+y+z=100. ) When producing the raw material powder of perovskite and its solid solution represented by In order to precipitate component A after regulating the concentration and pH of ions generated from the precipitate forming agent in the precipitate-containing liquid, the components that were difficult to precipitate 100% using the coprecipitation method are completely removed. In addition, as a result of obtaining a precipitate in which two or more phases are highly interdispersed, it is difficult to cause agglomeration during precipitate formation or coagulation during drying and calcination, resulting in a high bulk density and easy-to-sintered precipitate. A solid powder can be produced with good reproducibility.

In addition, in this process, each phase is highly mutually dispersed, so that the calcined material achieves sufficient uniformity. Furthermore, since the process is simple, it has excellent effects such as being able to obtain easily sinterable powder with good reproducibility and at low cost.

Claims (1)

[Claims] 1 General formula X[Pb(A _1/3 B _2/3 )O ₃ ]-y(PbTiO ₃ )-z
(PbZrO ₃ ) (where A represents at least one of Mg, Zn, Ni, and Co; B represents at least one of Nb and Ta; x, y, and z represent mol%; x
+y+z=100. ) When producing the raw material powder of the composite perovskite structure compound (hereinafter referred to as perovskite) and its solid solution,
After contacting each component solution of B, Pb, Ti, and Zr with a precipitate-forming solution to form precipitates of each component in a stepwise manner, the concentration of ions generated from the precipitant-forming agent in the precipitate-containing solution was 0.2 mol. The precipitate is washed so that the concentration of
An easily sinterable composite characterized by adding a hydroxide solution of component A to form a precipitate containing component A after adjusting the pH to 11.5 or higher, and calcining the resulting precipitate. A method for producing perovskite raw material powder.