JPH0471032B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a zirconate lead titanate-based sintered body, and in particular to a method for manufacturing a zirconate lead titanate-based sintered body that can be sintered at low temperatures and has high density and high strength. It is about the method. [Prior Art] Traditionally, lead zirconate titanate sintered bodies have been produced by the normal pressure method and the hot press method. In the normal pressure method, a preformed compact (green compact) and lead oxide or a compound containing lead oxide used to control the gas partial pressure of lead oxide in the crucible are placed in the crucible, and the crucible is sealed. It was heated and sintered. This normal pressure method for producing a lead zircon titanate sintered body cannot produce a dense lead zircon titanate sintered body when fired at a low temperature. Conversely, when fired at high temperatures, problems such as difficulty in adjusting the lead oxide gas atmosphere in the crucible and decomposition and melting of lead zirconate titanate arise. Furthermore, firing at high temperatures causes abnormal growth of lead zirconium titanate crystal grains,
This results in deterioration of electrical and mechanical properties. On the other hand, the conventional hot press method usually uses an alumina mold, and a filler such as alumina powder is placed around the preformed lead zircon titanate compact to prevent the reaction between the lead zircon titanate and the alumina mold. The sintered body was manufactured by compressing it under heat. This conventional manufacturing method has problems such as the need to hot press under high temperature and pressure in order to obtain a high-density lead zirconate titanate sintered body due to the poor slipperiness of the filler. There is. Note that Japanese Patent Publication No. 45-16869 discloses an invention in which a small amount of fluoride is blended into a piezoelectric ceramic composition to improve sinterability. However, this invention uses fluoride as a part of the piezoelectric porcelain, which changes the composition of the piezoelectric porcelain. [Object of the invention] The present invention enables sintering at a lower temperature than conventional methods.
A method for producing a lead zircon titanate molded body with improved sinterability, which allows a lead zircon titanate sintered body with higher density, higher strength, and excellent electrical properties to be obtained at the same sintering temperature. The purpose is to provide. [Structure of the Invention] The method for producing a lead zircon titanate sintered body of the present invention includes a step of molding a raw material powder that becomes a lead zircon titanate sintered body by sintering to obtain a molded body; This method is characterized by comprising a sintering process in which the body is sintered in the presence of a compound containing a fluorine element to obtain a sintered body. What is the zirconate lead titanate-based sintered body in the present invention?
The main component is PbZrTiO ₃ and is conventionally known as lead zirconium titanate piezoelectric porcelain. This lead zircon titanate sintered body has PbZrTiO ₃ as its main component, and some of the cations Pb, Zr, and Ti are Mn, Sb, Bi, Ta, W, Nb,
Y, Th, Ce, La, Ni, Co, Sr, Ca, Ba, Sn,
It may have a composition in which one or more types of Fe are substituted. Furthermore, the zirconate lead titanate-based sintered body has x+y+z=100 mol%.
PbTiO ₃ +y・PbZrO ₃ +z・Pb (Co _1/3 Nb _2/3 O ₃ may be used as the main component. In the production method of the present invention, the above-mentioned lead zirconate titanate-based sintered body can be obtained. A raw material powder is used. In the present invention, the raw material powder for the zirconate lead titanate-based sintered body is a conventionally known powder, but the present invention particularly uses a raw material for the zirconate lead titanate-based sintered body having a new composition. The raw material powder can also be calcined and used in the same way as before.
Further, the raw material powder may be granulated and used as necessary. As the compound containing the fluorine element to be present when sintering the molded article of the present invention, a synthetic compound or a natural substance having a fluorine component can be used. That is, fluorides, fluorine-based minerals, etc. can be effectively used. Specifically, CaF ₂ , BaF ₂ , CrF ₂ , MnF ₂ , CoF ₂ , NiF ₂ ,
_{MgF2 ,} PbF, _SrF , _{KMg3AlSi3O10F2 ,}
Examples include Na ₃ AlF ₆ . Note that the compound containing the fluorine element may be present as a mixture of other substances. Such materials include alumina, silica,
It may also be silicon nitride, silicon carbide, or a lead-containing compound such as lead oxide for adjusting the vapor pressure of lead oxide. The first step of the present invention is a step of molding the raw material powder of the above-mentioned lead zircon titanate-based sintered body to obtain a molded body. Compression molding, which compresses raw material powder in a mold, is usually used for this molding. The process itself for obtaining this molded body is the same as the molding process of the conventional method for producing a lead zirconate titanate-based sintered body. In the sintering step, the compact is sintered in the presence of the above-described compound containing the fluorine element. Sintering temperature requires 600-1300℃. In order to prevent lead oxide from scattering due to evaporation during sintering, it is preferable to allow sufficient lead oxide vapor to exist around the sintered body to prevent lead oxide from scattering. Furthermore, in order to cover the sintered compact with an atmosphere of fluorine components that may be scattered from the fluorine element-containing compound, the green compact and the fluorine-containing compound are placed in a closed container during sintering, as in the past. It is preferable to adjust the atmospheric gas inside the closed container. During this sintering, it is also preferable to pressurize the compact, so-called hot pressing. As for the hot press itself, an alumina mold or the like can be used as in the conventional case. In the case of this hot pressing as well, it is necessary to coexist a compound containing a fluorine element around the molded body. Specifically, it is used as part of a filler or as part of an auxiliary mold. The sintered body thus obtained may be subjected to heat treatment at normal pressure in a temperature range of 800 to 1300°C, if necessary. [Effect of the invention] According to the production method of the present invention, the same raw material composition,
When manufactured under firing conditions, the mechanical properties are improved by about 30% and the electrical properties are improved by about 10% using the normal pressure method. On the other hand, in the case of hot pressing, the mechanical properties are improved by about 50% and the electrical properties are improved by about 15 to 50% by manufacturing according to the method of the present invention. The detailed reason why the sinterability of the zirconate lead titanate-based sintered body is improved in the manufacturing method of the present invention is unknown. However, the inventor discovered that due to the high temperature during sintering, fluorine gas or fluorine compound gas was generated from the fluorine element-containing compound present with the compact, and that this fluorine gas, etc. , reacts to form a liquid layer of low melting point eutectic or fluorine-containing glass, and furthermore, the fluorine that formed this liquid layer acts as a catalyst, and the fluorine acts as a catalyst. We believe that this will accelerate sintering and produce a high-density sintered body. The present invention will be explained below with reference to Examples. Example 1 Commercially available PbO, ZrO ₂ , TiO ₂ ,
Weigh out oxides such as SrCO ₃ and wet mix them using a rubber-covered ball in a rubber-lined mill.
Eight types of raw material powders No. 1 to No. 8 were obtained. Next, these mixed raw material powders were preliminarily calcined at 950° C. for 5 hours, and wet-pulverized again in a ball mill for 24 hours. After drying, a small amount of polyvinyl alcohol aqueous solution was added as a binder and granulated, which was then molded into a disk shape with a diameter of 20 mm and a thickness of 13 mm using a press at a pressure of 700 kg/cm ² to obtain a molded body. In order to remove polyvinyl alcohol as a binder from these molded bodies, these molded bodies were heated in the atmosphere at 550° C. for 2 hours to decompose and vaporize the polyvinyl alcohol. Next, using the fluoride containing fluorine shown in Table 1 as a filler,

【table】

[Table] Each molded body was embedded in a fluoride in a crucible, the lid of the crucible was sealed, and firing was performed. The firing conditions are also shown in Table 1. The amount of filler used was approximately 50 g per molded body. The average particle size of the filler is 60 microns. Also, it says PZT.
Showing _PbZrTiO3 . In this way, eight types of zirconate lead titanate-based sintered bodies were obtained. The obtained zirconium titanate-based sintered body was 2 x 2 x 15 (mm) using a diamond wheel.
The sample was cut into pieces, the surface was ground, and the bulk density and bending strength were measured. Furthermore, 5×5× from the remaining part
It was cut into 0.5 (mm) pieces and the dielectric constant (ε) and dielectric loss (Tanδ) were measured. The bulk density was determined by the Archimedes method, and the bending strength was determined by a three-point bending method with a span of 10 mm. To measure the dielectric constant and dielectric loss, after applying silver paste to the surface of the cut sample,
It was baked at 550℃ and made into an electrode. After that, poling was performed in silicon oil at 4 KV/mm for 5 minutes to align the polarization. Measurements were performed using an LCR meter at a frequency of 1 KHz and a voltage of 1 V. The obtained results are also shown in Table 1. Table 1 also shows, as comparative examples, Nos. 101 to 109 in which sintering was performed under conditions in which no compound containing fluorine was present during sintering, and other conditions were substantially the same as in Example 1. The measurement results of a lead zirconium titanate-based sintered body obtained by sintering under the same conditions are also shown. The results shown in Table 1 will be discussed in detail. First No.1
Samples No. 4 and No. 101 to No. 103 and No. 108 have the same raw material composition and sintering conditions, and differ only in the filler. Obtained by the production method of the present invention
Samples No. 1 to No. have bulk densities of 7.1 to 7.3,
The bending strength is between 10.9 and 11.6Kg/ ^mm2 . On the other hand, samples No. 101 to No. 103 and No. 108 of Comparative Examples have a bulk density of 6.7 to 6.9 and a bending strength of 7.9 to 8.4 Kg/mm ² . As described above, the bulk density and bending strength of the lead zircon titanate sintered body obtained by the method of the present invention are approximately 30% higher than those of the lead zircon titanate sintered body of the comparative example. Also, regarding the electrical properties, the permittivity of samples No. 1 to No. 4 is from 1220 to 1220.
1310, whereas No.101 to No.103 and No.
The dielectric constant of sample 108 is low, ranging from 1130 to 1210. on the other hand,
The dielectric loss of samples No. 1 to No. 4 is 1.6 to 1.7 (×
10 ^-3 ), whereas samples No. 101 to No. 103 have
It is 2.0 to 2.0 (×10 ^-3 ). As described above, samples No. 1 to No. 4 obtained by the manufacturing method of the present invention have a higher dielectric constant and a smaller dielectric loss than the comparative samples No. 101 to No. 103 and No. 108. . In addition, regarding No. 5, No. 6, No. 104, No. 105, No. 109, and No. 7 and No. 106, which were obtained with the same raw material composition and the same sintering conditions, No.8 and
Regarding each sample No. 107, it can be seen that similarly, the samples obtained by the manufacturing method of the present invention have superior mechanical properties and electrical properties compared to the comparative example. Example 2 In the same manner as in Example 1, oxides were blended to have the composition shown in Table 2, and a molded article having a diameter of 35 mm and a height of 13 mm was similarly obtained. These molded bodies are
A filler powder consisting of a fluoride or a mixture containing a fluoride as shown in the table was added and then hot pressed. As a hot press type, the outer diameter is 90
An alumina mold with an inner diameter of 50 mm and a height of 65 mm was used. The bulk density, bending strength, dielectric loss, and dielectric constant of the lead zirconate titanate sintered body obtained by the hot pressing method were measured in the same manner as in Example 1. The results are also shown in Table 2. Table 2 also lists the test results of lead zirconate titanate sintered bodies obtained by hot pressing without using the substance containing the fluorine component of the present invention. As is clear from Table 2, the bulk density and bending strength of the sintered body of the zirconate lead titanate based sintered body hot-pressed in the presence of fluoride according to the present invention are the same as those of the comparative example. Just compare it to the body

【table】

[Table] A material with excellent electrical properties, high density, high bending strength, high dielectric constant, and low dielectric loss was obtained.

Claims (1)

[Scope of Claims] 1. A step of forming a raw material powder into a lead zircotitanate-based sintered body by sintering to obtain a compact, and sintering the obtained compact in the presence of a compound containing a fluorine element. A method for producing a lead zirconium titanate sintered body, comprising: a sintering process for obtaining a sintered body. 2. Claim 1 that the zirconate lead titanate-based sintered body is a sintered body whose main component is PbZrTiO ₃
Manufacturing method described in section. 3 Zircon lead titanate sintered body is PbZrTiO ₃
And some of the Pb, Zr, and Ti in the PbZrTiO ₃ are Mn,
Sb, Bi, Ta, W, Nb, Y, Th, Ce, La, Ni,
The manufacturing method according to claim 2, which is a sintered body having a composition in which one or more of Co, Sr, Ca, Ba, Sn, and Fe are substituted. 4 Zircon lead titanate sintered body contains a small amount of NiO,
The manufacturing method according to claim 3, which contains oxide components such as Fe ₂ O ₃ and ThO ₂ . 5. Claim 1, in which the molded body is sintered in the presence of one or a mixture of two or more of oxides, nitrides, and carbides containing fluorine-containing compounds.
Manufacturing method described in section. 6. The manufacturing method according to claim 1, wherein the molded body is sintered under pressure.