JPH05170555A - Production of ceramics - Google Patents

Abstract

PURPOSE:To provide a production process for ceramic material effective for reducing the warpage generated in the sintering of ceramic, facilitating the dissipation of a binder and decreasing the cracking defects. CONSTITUTION:One or more ceramic compacts are stacked one upon another and sintered to obtain a ceramic material. In the above process, a setter plate having a porosity of >=5% is placed on at least one part above or below the stacked compacts or between the compacts.

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 ceramics compact having a step of stacking and sintering the compacts, and more particularly, to reducing the warpage of the ceramics in the sintering step and simultaneously scattering the binder. The present invention relates to a method for manufacturing ceramics that facilitates the production of the ceramics and has less crack defects.

[0002]

2. Description of the Related Art When a ceramic plate-shaped molded body is fired, the sintered body generally warps. In order to reduce this, the ceramics compacts are arranged above or below the ceramics compact, which has the same composition as that of the ceramics compact, or ceramics plates of other materials having the same physical properties, or both. This ceramic plate is called a setter, and this setter minimizes warpage by wrapping and the like, and this surface accuracy reduces the warpage of the ceramic molded body during firing. The mechanism for reducing the warp of the molded body is as follows. The setter located on the upper side,
The weight presses the compact, which reduces warpage of the compact. In the setter arranged on the lower side, the ceramic becomes soft at a high temperature during firing, and the molded body is deformed by its own weight along the surface of the setter, so that the warp is eliminated.

[0003]

In the above-mentioned conventional method for producing ceramics, the warp of the molded body can be reduced, but since the upper and lower sides of the molded body containing the binder are sandwiched by the setters, the binder scatters. However, there is a problem in that the ceramics are reduced due to the remaining binder and the characteristics are deteriorated. Further, since the setter is used many times in the firing process, there is a problem that warpage occurs. To solve this problem, the thickness of the setter is increased to some extent to prevent warpage. However, accompanying this, the weight of the setter becomes too heavy, and there is a problem that cracks occur in the molded body during the firing process of the ceramic molded body.

The present invention has been made in view of the above-mentioned problems of the prior art. A ceramic which reduces warpage of the ceramic during the sintering process, facilitates scattering of the binder, and reduces cracking defects. It is intended to provide a method of manufacturing.

[0005]

The gist of the present invention is to provide a method for producing a ceramic having a step of stacking and sintering one or more ceramic compacts, wherein the compacts stacked in the sintering step are: It is characterized in that a plate-shaped setter is arranged at least at one place between the lower part and the molded body, and the porosity of the setter is 5% or more.

[0006]

The present invention increases the porosity of the setter to 5 as described above.
By making the setter more porous, the weight of the setter can be reduced, the load applied to the ceramic compact during firing can be reduced, and cracking in the firing process of ceramics can be reduced. Further, by making the setter porous, the setter is less likely to warp, the warpage of the molded body is reduced, and the decomposition gas of the binder contained in the ceramic molded body in the firing process is easily scattered through the pores. .

[0007]

EXAMPLES The present invention will be described in detail below with reference to examples.
An example of a method for forming a molded body from piezoelectric ceramics and firing the molded body will be described. First, a setter is made as follows by the same steps as those for producing the ceramic shown in FIG. Pb of PZT ceramics having the same composition as the piezoelectric ceramic compact to be fired
(Ti _0.48 Zr _0.52 ) O ₃ +1.0 wt% Nb ₂ O ₅ PbO, TiO ₂ , Zr
Powders of O ₂ and Nb ₂ O ₅ were weighed, and these powders were wet-mixed with a ball mill to prepare a slurry (step a).
The obtained slurry was dehydrated and calcined in an electric furnace at a temperature of 900 ° C. (step b). A polyvinyl alcohol (PVA) -based binder is added to the calcined powder in an amount of 5 relative to the calcined powder.
wt% and poly (methyl methacrylate) with a particle size of 50 μm (P
MMA) was added to the calcined powder in an amount of 10 wt% and wet mixed with a ball mill to prepare a slurry (step c). The slurry thus obtained was dried and granulated with a spray dryer (step d). This powder was pressed into a thin plate of 35 mm × 35 mm × 2.5 mm in thickness at a pressure of 1 ton / cm ² . This molded body is heated to 1250 ° C in an electric furnace.
By firing at the temperature of (step e), a porous sintered body having a porosity of 30% was produced (step f). In order to use this porous sintered body as a setter, flatness was obtained by wrapping.

Then, a molded body of piezoelectric ceramics is manufactured in the same manner as the setter by the process for manufacturing the ceramics shown in FIG. The piezoelectric ceramic has the same composition as the PZT-based ceramic of the setter described above, and is dried and granulated by a spray dryer in the same process as in the case of the setter except that PMMA for increasing the porosity is not added (step a. To d), the obtained powder was molded by press molding at a pressure of 1 ton / cm ² (step e) to obtain a thin plate-shaped compact of 25 mm × 25 mm × 0.8 mm in thickness. As shown in FIG. 2, the porous setters 2 and 2 are arranged on the upper and lower sides of the molded body 1 and are heated at 1200 ° C. for 2-4.
Firing was performed over time (step f). With respect to the fired body thus obtained, the crack defect rate and the electromechanical coupling coefficient (Kp)
Table 1 shows the results of testing for (%) and dielectric constant.
For comparison, Table 1 also shows the examples using the setters having a porosity outside the range of the present invention in columns f and g.

[0009]

[Table 1]

In the present embodiment, the composition of the setter and the composition of the material to be fired are the same, but different compositions may be selected with less reaction. Further, it may be applied to a dielectric material other than the piezoelectric material, an insulator, a magnetic material and other structural ceramics. The method of forming the pores in the setter is not limited to mixing the resin powders shown in the above examples,
In addition to the resin powder, a method of increasing the mixing ratio of the organic binder, mixing a foaming agent, and molding may be used. In addition, the molding method also shows an example of pressing the granulated powder by a spray dryer in the examples, but in the molding method such as sheet molding method such as doctor blade method and pull-up molding method, extrusion molding, injection molding, cast molding, A substance that makes pores after firing may be mixed.
Further, in the embodiment, the contaminants that form the pores are mixed in the slurry and granulated, but a method of mixing the granulated powder with the resin powder in a dry manner may be used. Further, in the above-mentioned examples, the explanation was made with the single-plate ceramics, but in the laminated body including the internal electrodes, the binder is particularly difficult to scatter, and the residual binder is often a problem, but the present invention is also effective in firing the laminated ceramics. Is.

[0011]

According to the manufacturing method of the present invention, in the fired ceramics, the decomposed gas of the binder smoothly scatters through the pores, so that the deterioration and reduction of the ceramic due to the residual binder can be eliminated. Further, since the weight of the setter can be reduced, cracking defects of the ceramic can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a process of manufacturing a ceramics according to the present invention.

FIG. 2 is a perspective view illustrating a firing step in the method for producing ceramics according to the present invention.

[Explanation of symbols]

 1 molded body 2 setter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Komatsu Kenji Komatsu 2 26-10 Tenjin Tenjin, Nagaokakyo, Kyoto Stock company Murata Manufacturing Co., Ltd. (72) Inoue Daizo 2 26-10 Tenjin, Nagaokakyo, Kyoto Murata Manufacturing Co., Ltd. (72) Tamara Matsuura, Inventor, 2 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Prefecture Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A method for producing a ceramic having a step of stacking and sintering one or more ceramic compacts, and at least one place above, below or between the compacts stacked in the sintering step. A plate-like setter is arranged on the substrate, and the porosity of the setter is set to 5% or more. 2. The method for producing ceramics according to claim 1, wherein the molded body is a laminated body having internal electrodes.