JPH0647462B2 - Method for producing complex oxide powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite oxide powder used as an electronic material ceramics such as a dielectric material and a piezoelectric material. The present invention relates to a manufacturing method that can be obtained.

[Conventional technology]

The composite oxide powder is generally produced by mixing powders of respective components or precursors thereof, molding and firing.
In this method, the raw material powders that are physically and uniformly mixed are fired to cause a solid-phase reaction to form the target complex oxide powder.

However, in this method, the solid-phase reaction proceeds slowly, and it is difficult to make the composition uniform. Therefore, it is necessary to repeatedly perform calcination and pulverization several times, it is difficult to prevent the inclusion of impurities in the process, it is difficult to obtain a high-purity powder, as a result, its electrical characteristics, for example, as a piezoelectric body, a dielectric body. The characteristics of the device deteriorate and vary. Further, when lead is contained as its component, deviation from the stoichiometric ratio due to volatilization of lead during firing becomes a serious problem.

Therefore, in order to obtain a finer powder, the ingredients are more evenly dispersed, and a wet coprecipitation method or a metal alkoxide is used as a starting material.
By its hydrolysis and heat treatment of the obtained amorphous powder,
Pb (Zr _X Ti _1-X ) O ₃ (0 ≦ X ≦
1) Attempts have been made to produce powder.

[Problems to be Solved by the Invention]

However, it is difficult to make the powder fine by the method of mixing and firing the powders of the respective components, and it is difficult to completely react the respective components with each other during the solid phase reaction.

In the wet coprecipitation method, it is difficult to set the conditions for coprecipitating multiple components at a target composition ratio at the same time, and as a result, the composition of the composite oxide powder precursor deviates from the target composition and the characteristics of the final product ceramics are Make it worse.

According to Japanese Patent Laid-Open No. 63-282123 and Kasai et al. (Journal of the Ceramic Society of Japan, 96 [2], 140 (1988)), Pb (Zr _X Ti _1- It becomes possible to produce an _X ) O ₃ precursor sol, and the composite oxide having the above composition can be synthesized at a lower temperature than the solid phase method. However, the lead alkoxide used in these methods is very expensive and has a very high hydrolysis rate, so that it must be handled with care. Further, the obtained powder is amorphous, and heat treatment at 600 ° C. or higher is required for crystal formation.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a simpler method for producing a complex oxide powder at a lower temperature.

[Means for Solving the Problems]

The present invention, in the method for producing a complex oxide powder represented by the structural formula Pb (Zr _X Ti _1-X ) O ₃ (0 ≦ X ≦ 1), in alcohol,
An alkoxide of Zr and / or Ti is reacted with lead acetate by heating, and the reaction solution of the heating reaction is diluted with a solvent containing a polar functional group in the molecule and having no active hydrogen, and then hydrolyzed with an alkaline solution. A method for producing a complex oxide powder, characterized by decomposing.

The present invention will be described in detail below.

The alcohol used is preferably one having a C number of 1 to 4 in consideration of the ease of removal after hydrolysis. Zr and / or Ti
The alkoxide (hereinafter, abbreviated as Zr / Ti alkoxide) is not particularly limited, but is preferably one having 1 to 4 carbon atoms depending on the metal content.

The reaction between Zr / Ti alkoxide and lead acetate is preferably carried out at the reflux temperature of the alcohol used to complete the reaction as quickly as possible = boiling point (for example, in methanol, ethanol, 1-propanol and 1-butanol, each is about , 65, 80, 100, 120 ° C.), and the reaction time is determined by the Zr / Ti ratio. For example,
It takes from several hours to tens of hours.

Further, the concentration of Zr / Ti alkoxide during this reaction is not particularly limited as long as the reaction product is soluble, and is appropriately selected depending on the type of alkoxy group, solvent and the like.

In the present invention, the reaction solution containing the obtained reaction product is diluted, and a solvent containing a polar functional group in the molecule and having no active hydrogen is used as a diluting solvent at this time. .

The diluent solvent contains a polar functional group in the molecule and does not have active hydrogen, that is, an acetic acid group (CH ₃ COO) remaining in the heated reaction product of Zr / Ti alkoxide and lead acetate. ,
It does not cause a substitution reaction such as an exchange reaction with the metal such as an alkoxy group and a covalent bond, and the functional group has a function to stably exist the fine particles of initial hydrolysis generated by the heating reaction product. As a matter of course, it is preferable that the fine particles have a smaller dissolving power than alcohol as the initial solvent. In particular, a solvent having a carbonyl group or a nitrile group in the molecule is preferable.

Examples of the diluting solvent include ketones such as acetone and methyl ethyl ketone as those having a ketone group as a functional group, and those having an ester group as a functional group such as methyl acetate and ethyl acetate. Examples thereof include esters, and examples of those having a nitrile group as a functional group include nitriles such as ethanenitrile (acetonitrile) and butanenitrile.

Further, the dilution rate of the reaction solution is appropriately determined depending on the Pb, Zr / Ti concentration, the type of alkoxy group, the type of diluent solvent, the pH value and the like.

The amount of water used for the hydrolysis with the aqueous alkaline solution in the present invention is 2 to 200 mol times, preferably 2 to 100 mol times Zr and / or Ti.

Examples of the alkali of the alkaline aqueous solution include inorganic non-metal compounds such as ammonia, alkali metal hydroxides such as NaOH and KOH, and basic organic substances such as amines, etc., but containing no metal element as an impurity, and Ammonia water is particularly preferable because it is easily removed. PH of alkaline aqueous solution
Is preferably adjusted to a range of 8-14.

Especially when ammonia water is used, its concentration is Zr / Ti.
Determined by the type of alkoxide and the Zr / Ti ratio,
It is generally in the range of 0.01N to 10N.

Ammonia water is particularly preferably used as a solution after being diluted with the above-mentioned diluent solvent or alcohol solution.

The powder obtained by the hydrolysis in the present invention is amorphous, but becomes a crystalline powder having a perovskite structure by a heat treatment at 250 ° C. or higher and within 1 hour.

[Action]

By heating lead acetate and Zr / Ti alkoxide to react with each other, a chemical bond is formed between them and a Pb-Zr / Ti composite precursor is formed. As a result, it is considered that the chemical bond was retained even after hydrolysis, and a fine powder containing a stoichiometric ratio of lead was produced. The obtained powder becomes an amorphous powder because acetic acid groups and hydroxyl groups remain in the particles or on the surface of the particles. However, it is considered that the precursor structure is similar to the crystalline state, and the crystalline powder having the perovskite structure can be easily obtained at low temperature due to elimination of the acetic acid group and the hydroxyl group.

By diluting with a solvent that contains a polar functional group in the molecule and does not have active hydrogen, the solubility of the initial product of hydrolysis will decrease moderately, and by addition of an alkali such as ammonia, a polycondensation reaction will occur. It is considered that the powder was promoted and a better powder was obtained. Hydrocarbons such as benzene and hexane cannot obtain a good powder because of rapid agglomeration of particles. In other words, C = in the above diluted solvent molecule
Polar functional groups such as 0 and CN groups are involved in particle growth and dispersion and contribute to stabilization of particles. On the other hand, when only alcohol was used as a solvent or when it was hydrolyzed with water having a pH of 7 or less, a sol or a gel was obtained, and the crystallization temperature of this precursor was higher.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples. However,
The invention is not limited to these examples.

Example Lead acetate anhydrous and tetraethoxy titanium (Sample No. 2
4: PT system), lead acetate anhydride, tetraethoxy titanium and tetrabutoxy zirconium (Sample No. 8: PZT system, Zr / Ti)
= 1) and lead acetate anhydride and tetrabutoxyzirconium (Sample No. 10: PZ system) were refluxed in ethanol for 12 hours. Acetone, methyl acetate, or acetonitrile as a diluting solvent was added in a predetermined amount (described in the margin of Table 1 below), and then ammonia water having a concentration shown in Table 1 was added to cause hydrolysis to obtain a white powder. By heating at the crystal formation temperature shown in Table 1 below, the grain size of 0. A crystalline white powder of ˜0.3 μm was obtained. The conditions and results are shown in Table-1.

Comparative Example 1 Lead acetate anhydride and tetraethoxy titanium (Sample Nos. 5 and 6: PT system) were refluxed in ethanol for 12 hours. After adding benzene and hexane as the second solvent, aqueous ammonia was added for hydrolysis. The product was an agglomerated gel. The conditions and results are shown in Table-1. Crystal formation was observed in the aggregated gel at 250 ° C, but heat treatment at 500 ° C is required to obtain the same degree of crystallinity as Sample Nos. 3 and 4 when using this diluted solvent. Met.

Comparative Example 2 Lead acetate anhydride and tetraethoxy titanium (Sample No. 1: PT
System), lead acetate anhydride, tetraethoxy titanium and tetrabutoxy zirconium (Sample No. 7: PZT system, Zr / Ti = 1)
) Or anhydrous lead acetate and tetrabutoxy zirconium (Sample No. 9: PZ system) were refluxed in ethanol for 12 hours. Distilled water was added for hydrolysis, and sample Nos. 1 and 7 and 9
To obtain a sol. A gel was formed by removing the solvent. Table 1 shows the conditions such as the crystallizing temperature and the results.

The metal concentrations in the table are Pb or Zr and / or Ti concentrations (mo
l /).

[Advantages of the Invention] According to the present invention, a composite oxide represented by a structural formula Pb (Zr _X Ti _1-X ) O ₃ (0 ≦ X ≦ 1) of high purity, which is uniform and fine and has no compositional deviation. The powder can be obtained in a simple manner and at low temperature.

Claims (3)

[Claims] 1. A method for producing a composite oxide powder represented by the structural formula Pb (Zr _X Ti _1-X ) O ₃ (0 ≦ X ≦ 1), wherein an alkoxide of Zr and / or Ti is added in alcohol. A complex characterized in that it is reacted with lead acetate by heating, the reaction solution of the heating reaction is diluted with a solvent containing a polar functional group in the molecule and having no active hydrogen, and then hydrolyzed with an alkaline solution. Method for producing oxide powder. 2. The method for producing a composite oxide powder according to claim 1, wherein the solvent is selected from the group consisting of ketones, esters and nitriles. 3. A method for producing a composite oxide powder, wherein aqueous ammonia is used as the alkaline aqueous solution.