JPH06100364A - Production of lead titanate zirconate-based high density ceramic - Google Patents

Abstract

PURPOSE:To provide a method for economically producing the lead titanate zirconate-based ceramic by a liquid phase sintering method using a lead halide solid solution or a lead halide lead oxide solid solution as a sintering auxiliary. CONSTITUTION:A lead titanate zirconate calcination powder is mixed with the powder of a solid solution comprising different kinds of lead halides or the powder of a solid solution comprising a lead halide and a lead oxide in an amount of 1-60mol.% based on the amount of the lead in the calcination powder, and subsequently molded. The molded product is melted and simultaneously sintered at an arbitrary temperature in the range of the melting point of the solid solution to <=900 deg.C to provide the lead titanate zirconate-based ceramic. Since the solid solution is melted in the sintering process for forming liquid phases between the calcination powder particles and since the constituting substances in the calcination powder are transferred through the liquid phases, the sintering of the calcination powder can thereby be accelerated in a low temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a homogeneous and high-density lead zirconate titanate-based ceramics. Lead zirconate titanate-based ceramics have a high dielectric constant,
The feature is that the piezoelectric property is large. In addition, because of the high reliability of various properties of materials, various applications in the fields of electronics and mechanoelectronics are possible. For example, by utilizing its ferroelectricity, it can be used as a capacitor material, and by utilizing piezoelectricity it can be used for various ultrasonic vibrations. A wide range of practical uses are known to children. Furthermore, the addition of lanthanum makes it possible to exhibit translucency, and its electro-optical characteristics are expected to be applied to the main members of optical shutters and optical memories.

[0002]

2. Description of the Related Art Conventionally, as a method for producing lead zirconate titanate-based ceramics, a starting material having a predetermined stoichiometric ratio is used, and a dry method or a wet method (alkoxide method, coprecipitation method, compound precipitation method, Slurry mixing method, etc.) and heat to obtain a calcined powder, which is then crushed and molded into a powder compact, which is then subjected to hot isostatic pressing or normal pressure firing. Various methods are known for sintering to produce a final product.

In these manufacturing methods, various measures have been taken in order to prevent the composition change due to volatilization of the lead component which is likely to occur in the sintering process. That is, an excess amount of lead component compared to the stoichiometric amount is added to the starting material in advance, or a powdered lead compound is sealed and sintered together with a compact in a platinum crucible, or composed of a lead compound. A technique is also known in which a molded body is placed in a container and sintered. Therefore, these techniques require a container made of a platinum crucible or a lead compound, and the sealing work of the lead compound in the platinum container has been a major obstacle in mass production.

JP-A-3-295859 has been proposed for the purpose of improving the drawbacks of the conventional manufacturing method. This is a liquid-phase sintering of the calcined powder by adding lead halide powder as a sintering aid. Due to the effect of this sintering aid, it becomes possible to sinter at a temperature lower than the melting point of lead oxide, and therefore the production method is characterized in that the amount of lead volatilized is small. By this method, ceramics sufficiently sintered at a low temperature of 900 ° C. or less can be obtained, and many advantages such as eliminating the need for pollution prevention equipment against the generation of lead vapor have come to be known.

[0005]

On the other hand, it is generally considered that the higher the setting of the sintering temperature in the liquid phase sintering is, the more the sintering rate is accelerated. If it is set too high, the volatilization of lead becomes intense and the liquid phase decreases. As a result, sintering via the liquid phase is hindered and it becomes difficult to densify the structure. Therefore, the setting of the sintering temperature is limited by the liquid phase formation temperature. Further, since the melting point of lead halide is a unique value, for example, lead fluoride is 855 ° C., lead chloride is 501 ° C., lead iodide is 402 ° C., and lead bromide is 373.
Since it is ℃, the temperature setting of liquid phase sintering cannot be freely selected. Therefore, even with this method, there was a problem in that the setting of the sintering temperature was limited. An object of the present invention is to improve the drawbacks found in the above-mentioned conventional manufacturing techniques of lead zirconate titanate-based ceramics, to obtain titanium having high dielectric properties, excellent piezoelectric characteristics, electro-optical characteristics, and stable quality. An object of the present invention is to provide a method for producing a lead zirconate acid-based ceramics more economically.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and found that different types of sintering aids were used in the manufacturing process of the lead zirconate titanate ceramics. It was found that the above object can be achieved by using the solid solution powder of lead halide or the solid solution powder of lead halide and lead oxide.

The effects of the present invention will be described in more detail below. The components of the solid solution used as the sintering aid are lead halides and lead oxides, and lead fluorides include lead fluoride, lead chloride, lead iodide, and lead bromide, and lead oxides include lead oxide. Can be used. The composition ratio of the solid solution powder is determined on the basis of the phase diagram of the solid solution by determining the liquid phase formation temperature from the desired sintering temperature. The phase diagram is, for example, National
Bureau of Standards (USA)
Edited by the American Ceramic Soc
Book Phase Diagra published by iety
It is published in ms for Ceramics.

The melting point of these solid solutions is 270 to 900 ° C.
In order to obtain a desired temperature, the composition ratio can be determined from the phase diagram and the liquid phase formation temperature can be arbitrarily selected within the above range. The addition amount of the solid solution to the calcined powder can be selected within a wide range, but a small amount does not show the above-mentioned sintering promoting effect remarkably, and addition in a large amount deteriorates the above-mentioned various properties of the product, and economically. Since it is not preferable in terms of environmental protection, the lead content in the calcined powder raw material should be 1 to
It is necessary to be in the range of 60 mol%, but it is preferable to use it in an amount of 3 to 30 mol% in consideration of its economical efficiency. The lead zirconate titanate-based calcination powder raw material can be used regardless of its manufacturing method. In addition, various known techniques can be appropriately used in the crushing step and the subsequent molding, heating, and sintering steps.

Although the reaction mechanism of the production method of the present invention has not been completely clarified, it is considered as follows. Since a solid solution consisting of different kinds of lead halides or a solid solution consisting of lead oxide and lead halides is added to and mixed with the lead zirconate titanate-based calcined powder raw material, the solid solution melts at the melting point of the solid solution during the heating and sintering process. A liquid phase is formed between the calcined powder particles, and the migration and precipitation of the component substances of the lead zirconate titanate-based particles progress through this liquid phase. Therefore, it is considered that the sintering of the lead zirconate titanate-based calcined powder raw material is significantly promoted in a relatively low temperature range.

Thus, lead zirconate titanate-based ceramics having a high density and a high light transmittance, excellent electro-optical characteristics, fusible properties or piezoelectric characteristics, and stable quality between production lots can be easily obtained. it can. The economic effect is clear because the heat treatment temperature during liquid phase sintering can be set arbitrarily in relation to the melting point of the solid solution.

[0011]

EXAMPLES The present invention will be illustrated below with reference to Examples and Comparative Examples. (Example) Preparation of solid solution Lead fluoride and lead oxide powders were mixed in a ball mill at a molar ratio of 1: 9, calcined at 450 ° C for 1 hour, and then pulverized by a raker machine to obtain solid solution 1 and lead chloride. And lead bromide powder 1: 3
Ball-milled at a molar ratio of 1, and calcined at 400 ° C. for 1 hour, and then pulverized with a raider machine to solid-solution 2, and lead-iodide and lead-bromide powders were ball-milled at a molar ratio of 1: 9,
A solid solution 3 was prepared by calcination at 350 ° C. for 1 hour and then crushed by a raker. Sintering commercial PLZT calcined powder material (predetermined composition:. Pb _{0 91} La
_{. 0 09 (Zr 0 65 Ti} 0 35..) 0 9775 O 3 excessive addition Pb:. 2
% By weight, manufactured by Hayashi Chemical Industry, trade name (HIJIRCO
T)) is divided into three parts, and solid solutions 1, 2, and 3 of 10% of the lead component in the calcined powder raw material composition are added to each, and acetone is used as a medium separately in a ball mill using a polyethylene pot and a zirconia ball. Was mixed for 20 hours and wet pulverized. Then, these pulverized calcined powders were dried, granulated, put into a rubber mold (φ = 35 mm), and pressure-molded by a cold isostatic method. The obtained molded body was put into an alumina crucible and heated to give a solid solution 1 of 830 ° C. and a solid solution 2 of 54.
0 ° C., the solid solution 3 is kept at 440 ° C. for 15 hours, the added solid solution is melted to accelerate the sintering, and then 1150 ° C.
Was held in an oxygen stream for 20 hours to volatilize the above solid solution and perform solid phase sintering. The light transmittance of each sample (thickness 1.0 mm) obtained by mirror-polishing the obtained PLZT ceramics was measured by a spectrophotometer (Model 320 manufactured by Hitachi, Ltd.). As a result, 63 samples to which solid solution 1 was added at a wavelength of 600 nm were obtained. 0.0%, 65.0% for the sample to which solid solution 2 was added
%, The sample to which solid solution 3 was added showed a high transmittance of 65.5%.

COMPARATIVE EXAMPLE Commercially available PLZT similar to the example
Specimen-polished sample of PLZT ceramics obtained by mixing, pulverizing, drying, and shaping the calcined powder raw material under the same conditions as in Example without adding a solid solution, and firing at 1150 ° C. for 20 hours in an oxygen stream ( When the light transmittance was measured in the same manner as in the example for a thickness of 1.0 mm), the transmittance was 55.0% at a wavelength of 600 nm, which was lower than the example.

Although the examples of the present invention have been described in comparison with the comparative examples, the method for producing the lead zirconate titanate-based ceramics of the present invention is not limited to the above examples. A calcination powder raw material with a starting material having a predetermined theoretical composition to which is not added, or various known lead zirconate titanate-based calcination powder raw materials having different theoretical compositions are used, which deviates from the technical idea of the method of the present invention. Various modifications can be made within the range that does not.

[0014]

As described above, the method for producing lead zirconate titanate-based ceramics according to the present invention comprises a solid solution powder composed of different kinds of lead halides or a lead halide and lead as a raw material for a lead zirconate titanate calcinated powder. This is a method in which a solid solution powder made of an oxide is added and mixed, shaped, and then heated to melt and sinter the solid solution powder, so that the sintering promoting effect is remarkable and the liquid phase firing is associated with the melting point of the solid solution. This is an economical method because the heat treatment temperature at the time of setting can be set arbitrarily, and it is easy to manufacture high-density lead zirconate titanate-based ceramics with excellent light transmittance, electro-optical properties, dielectric properties, and piezoelectric properties. can do.

Claims (1)

[Claims] 1. A method for producing lead zirconate titanate-based ceramics by adding a sintering aid to a calcined powder and sintering the mixture, comprising different types of lead halides as the sintering aid. A method for producing a lead zirconate titanate-based ceramics, which comprises using a solid solution powder or a solid solution powder comprising a lead halide and a lead oxide.