JPH0678188B2 - Method for producing lead zirconate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing lead zirconate (PbZrO ₃ ).

Lead zirconate is expected to be used in a wide range of applications such as digital displacement elements and shape memory materials, and as raw materials for multicomponent piezoelectric ceramics such as PbZrO ₃ -PbTiO ₃ .

[Conventional technology]

Even if the lead zirconate powder is produced by the dry method using the oxide raw material powders (PbO powder and ZrO ₂ powder) that are the constituents of lead zirconate, the average particle size is 1 to 2 μm or more. It is difficult to obtain a porcelain having a high density and a high function by using the lead zirconate powder having such a particle size.

[Problems to be solved by the invention]

The present invention has been made to solve the above-mentioned drawbacks in the synthesis of lead zirconate by the dry method, and an object thereof is to produce a modified sub-micron grade modified zirconia raw material powder having good dispersibility and use the powder. It is an object of the present invention to provide a method of producing a lead zirconate porcelain having a high sinterability and a high density by a simple dry method.

[Means for solving problems]

The present inventors have earnestly studied to achieve the above object, in the process of producing lead zirconate represented by PbZrO ₃ ,
When a solution containing an appropriate amount of lead and zirconium is prepared and a hydrolysis reaction is carried out in the solution to produce a sol, the Zr-containing particles are less likely to aggregate due to the non-uniformity of the system, and the sol body obtained thereafter It was found that the powder was dried and calcined at 700 to 1300 ° C to obtain a submicron-class powder (modified zirconia powder) with extremely few agglomerates. Using this as the raw material, the remaining lead compounds of the target lead zirconate are mixed by a dry method, and if calcined, a raw material powder having excellent submicron-class powder characteristics can be easily obtained, and if this is molded, High-density lead zirconate porcelain can be easily obtained by simple solid-phase sintering without operations such as hot pressing and HIP (hot gas pressure sintering), and without necessarily requiring a sintering aid. Could be determined. The present invention has been completed based on this finding. The gist of the present invention is a combination of the following three steps (a to c).

(A) an appropriate amount of lead that constitutes lead zirconate,
A solution containing zirconium is prepared, and a hydrolysis reaction is carried out to form a sol.
Step of calcination at 0 ° C. In this step, a modified zirconia is obtained which avoids agglomeration in the sol living body and can be used for production of PZT, PLZT and the like.

(B) Mixing the calcined product obtained in step (a) with the remaining lead compound of the intended lead zirconate composition, and mixing it with 500 to 100.
Step of calcination at 0 ° C. In this step, the desired lead zirconate composition is obtained.

(C) A step of molding the obtained calcined powder and sintering at 700 ° C to 1400 ° C.

Examples of compounds for preparing the zirconium solution include zirconium oxynitrate and zirconium nitrate.

As a solvent for the zirconium solution, water or alcohol that dissolves the above compound is used. Furthermore, in order to prepare a zirconium solution, metallic zirconium can be dissolved in aqua regia or HF and used.

Lead compounds include lead nitrate [Pb (NO ₃ ) ₂ ] and lead chloride [PbCl
₂ ] and lead sulfate [PbSO ₄ ], but lead nitrate is preferred. A lead solution obtained by dissolving the lead compound in a solvent of water or alcohol can be prepared separately from the zirconium solution. Alternatively, the lead compound and the zirconium compound may be dissolved in the same solvent.

The hydrolysis reaction is carried out under heating (around 100 ° C), and the sol is collected by filtration and washing.

The amount of lead dissolved in the zirconium-containing solution is preferably in the range that can effectively suppress the agglomeration of the zirconia powder. The calcination temperature of the obtained coprecipitate is 700 to 1300 ° C. If the temperature is lower than 700 ° C, agglomeration will occur remarkably, and if it exceeds 1300 ° C, the particles tend to become coarse. To the powder thus obtained, the target lead zirconate deficient lead compound is added and mixed.

The calcination temperature of these mixtures must be above the minimum temperature at which the solid-phase reaction is almost or completely completed, and within the maximum temperature range where significant particle growth does not occur.
The range of 0 ° C is preferred.

The powder thus obtained is molded and sintered. The sintering temperature is generally in the range of 700-1400 ° C. If it is lower than 700 ° C, the sintering is insufficient, and if it exceeds 1500 ° C, the particles become coarse, or the constituent components volatilize.

〔Example〕

43.57 cc of lead nitrate aqueous solution (0.751 mol / l concentration) and 150 cc of zirconium oxynitrate aqueous solution (0.873 mol / l concentration) were mixed. By holding this mixed aqueous solution at 100 ° C. for 100 hours, a hydrolysis reaction was performed to obtain a sol containing Pb ²⁺ and Zr ⁴⁺ . This is washed and dried, and then calcined at 1100 ° C, (Pb
_0.2 Zr _0.8 ) O _1.8 powder was prepared. The powder was submicron grade particles.

1.4322 g of the powder, and 1.3391 g of commercially available PbO powder were mixed in a ball mill for one day and then calcined at 850 ° C. for 2 hours to obtain a PbZrO ₃ powder. The average particle size was 0.48 μm. This powder was molded at 1 ton / cm ² and then sintered at 1200 ° C. for 2 hours in a lead vapor / oxygen gas coexisting atmosphere. The density of the obtained porcelain was 7.96, which was extremely close to the theoretical density.

[Comparative example]

Commercially available PbO powder and ZrO ₂ powder were mixed to have a composition of PbZrO ₃ . The mixture was mixed with a ball mill for a whole day and night, and then calcined at 850 ° C. for 2 hours. 1 ton / cm ^{2 of the} obtained powder
Molded in a lead vapor / oxygen gas coexisting atmosphere at 1200 ° C for 2
Sintered for hours. The density of the obtained porcelain was about 6.2.

The powder obtained by calcination consists of large aggregates,
The average particle size could not be specified.

〔The invention's effect〕

According to the method of the present invention, the zirconia powder (modified zirconia powder) containing an appropriate amount of the lead compound which is the constituent of lead zirconate can be formed into submicron particles having extremely few secondary particles by the first step (a). , By using this, by using a simple dry method thereafter, a submicron class lead zirconate raw material powder can be easily obtained, and from this, a high density porcelain extremely close to the theoretical density can be obtained.
It can be obtained with the excellent effect. In addition, the following effects can be obtained.

(1) Since the modified zirconia powder obtained by calcination is sufficiently dispersed, it can be supplied as a raw material powder without requiring a pulverization step of the calcined product.

(2) Lead zirconate powder obtained by a dry method from the calcined modified zirconia powder is also obtained in a monodispersed state, and therefore has sufficiently easy sinterability and high density even if the pulverizing step is omitted.

(3) Lead zirconate porcelain, which requires extremely high density, can be obtained by simple solid-phase sintering without hot pressing or HIP (hot gas pressure sintering), and by using a sintering aid. A high density that is very close to the theoretical density can be obtained without the need.

(4) By mass-producing modified zirconia powder having excellent powder characteristics, high-performance lead zirconate porcelain can be supplied at extremely low cost.

Claims (1)

[Claims] 1. A solution containing (a) zirconium and an appropriate amount of lead that constitutes lead zirconate represented by PbZrO ₃ is prepared, a hydrolysis reaction is performed to form a sol, and the sol body is dried. Calcining at 700 to 1300 ° C, (b) mixing the calcined product with the remaining lead compound of the desired lead zirconate composition and calcining at 500 to 1000 ° C, (c) obtaining A method for producing lead zirconate, comprising the step of molding the obtained calcined powder and sintering at 700 to 1400 ° C.