JPS6214955B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a lead-based piezoelectric material, and an object thereof is to manufacture a smooth and high-density piezoelectric sheet. Recently, piezoelectric ceramics have been applied to a wide variety of fields, and their density and miniaturization have rapidly progressed. Conventionally, piezoelectric elements in a predetermined shape according to the application have been supplied by cutting and polishing sintered bodies or single crystal ingots, but this has resulted in deterioration of electrical characteristics due to processing distortion and processing costs. The problem is that it is expensive. For this reason, it is desired that elements having a desired shape can be supplied at low cost at the same time as they are fired through process simplification, mass production, etc.
In general, a known method for manufacturing sintered sheets is to knead ceramic material with a binding substance, mold it, create a green sheet of a certain thickness, punch it into a predetermined shape according to the intended use, and then sinter it. .
However, in sintered sheet products after firing, shrinkage during firing causes deformation, cracks, warping, perforations, pores, and even non-uniform composition, which has a significant impact on mechanical and electrical properties. There's a problem. In order to obtain high-performance, high-precision sintered sheets, it is necessary to increase the density of the raw sheet as much as possible.To do this, it is necessary to control the particle size of the raw material, and to add a small amount of binder and plasticizer to the ceramic material. Thoroughly kneading with a solvent to ensure good dispersion of the ceramic material, as well as uniform thickness and sufficient flexibility.
It is important that punching is easy and that no processing distortion remains. Regarding the amount of piezoelectric material containing lead, it is necessary to carefully consider the temperature, atmosphere, packing method, etc. in the firing process. Ceramics are generally sintered at high temperatures, and lead oxide evaporates at temperatures above about 800°C, leading to deterioration of piezoelectric properties. Particularly in the case of sheet-shaped ceramics, since the surface area is large compared to the volume, evaporation of lead occurs actively, making it difficult to sinter the sheet itself in the atmosphere. On the other hand, as a method of suppressing lead evaporation, there is a method of firing the element in a lead vapor atmosphere, but maintaining the sheet in a sealed state becomes undesirable in terms of cost and causes problems in terms of piezoelectric properties. The present invention provides a method for inexpensively producing a lead-based piezoelectric sintered sheet having high density, high homogeneity, and excellent smoothness. The method of the present invention uses raw sheets with high density and good smoothness, coats the raw sheets uniformly with a high-temperature oxide to enable lamination firing, and laminates the sheets in several stages to increase the specific surface area of the sheets. The method of the present invention dramatically improves sinterability, suppresses lead evaporation, and sinters in a sealed structure or similar structure. A lead-based piezoelectric sintered sheet with excellent properties can be obtained. In the method of the present invention, a predetermined amount of organic components such as a binder, a plasticizer, and a solvent are added to a lead-based piezoelectric ceramic material and kneaded, and this kneaded product is processed by a doctor blade method to a thickness of 0.05 to 2.0 mm depending on the application. After producing a high-density green sheet with a certain thickness and punching it into the required shape, it is placed in a container filled with powder of a high melting point oxide (at least one of zirconium oxide, magnesium oxide, and aluminum oxide). (It is preferable that the sheet and the powder come into good contact with each other.) The container is heated to a temperature at which the organic matter in the formed sheet does not deteriorate, and vibration is applied. By heating, the thermoplasticity of the organic material appears, making the sheet softer and making it easier for powder to adhere to it. By applying vibration to this, the sheet is charged and the oxide powder is mechanically rubbed in, and the powder adheres to the sheet surface. Several of these sheets are stacked together, placed on a heat-resistant substrate such as alumina, covered with a crucible, and placed in an electric furnace. Next, the temperature is maintained at a low temperature until the resin removal is completed, and then it is fired at a temperature of 1150 to 1350°C and the temperature is lowered to room temperature at a constant cooling rate to produce a sintered sheet. The lead-based piezoelectric ceramic material used in the method of the present invention may be a single-component type, a two-component type, or a three-component type consisting of a perovskite type compound or a tungsten bronze type compound. As an organic binder,
polyvinyl butyral, polyvinyl alcohol,
Examples include polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, methyl cellulose, ethyl cellulose, and polyvinyl acetate and polyvinyl butyral are particularly preferred from the viewpoint of adhesive properties. The plasticizer is selected depending on the binder, and for example, phthalate-based dibutyl phthalate, dioctyl phthalate, dioctyl adipate, glycerin, polyethylene glycol, etc. are used. The moldability, workability, and amount of powder deposited on the green sheet are preferably determined by taking into account the balance between the two, since a high density sheet cannot be obtained as a sintered body, although it is preferable that the binder and plasticizer are as large as possible. The optimum amount is 0.5 to 5.0 wt% for each, and the solvent is preferably water, alcohol, or an ether or ester type of polyhydric alcohol. A slurry is made with these voltage-sensitive ceramic materials, a binder, a plasticizer, and a solvent. This slurry is poured onto a smooth substrate such as an organic film, formed into a sheet of constant thickness using a doctor blade method, and dried to produce a smooth raw sheet. The green sheet may also be produced using other methods, such as extrusion or roll rolling. Next, the raw sheet is punched into the desired shape. The punched raw sheet contains organic components, so it is easily charged with static electricity. High-temperature oxide powder (zirconium oxide, magnesium oxide, aluminum oxide) is used as a material for refractory bricks and baking powder, and is a thermally stable material that adheres to charged objects. There is a proportional relationship between the charging voltage, the amount of adhesion, and the particle size that can be attached. In addition, since the sheets are charged by rubbing, the sheets overlap each other, and if there is powder between them, they will adhere to each other. Adhesion by static electricity alone requires a high charging voltage, and has the disadvantage that the sheets stick to each other and cannot be peeled off. For this reason, it is desirable to deposit with as low a charging voltage as possible. In addition to the method of adhering using vibration, heating the raw sheet softens it because the organic binder and plasticizer contained in the sheet have thermoplasticity. Powder easily adheres to the softened raw sheet. By using these in combination, the powder of the piezoelectric material is sufficiently adhered during firing, and lead evaporation occurs at 800°C, so that the sheets are fused together.
Since the attached powder is inert, it prevents fusion and makes it easier to peel off after firing. Raw sheets coated with powder are stacked and placed in an electric furnace. After preliminary firing to remove organic components, main firing is performed at a temperature of 1150 to 1350°C. In this case, at a temperature lower than 1150°C, sufficient sintering does not occur, and at a temperature higher than 1350°C, a composition shift occurs or decomposition occurs, and a single phase cannot be formed. After the main firing is completed, the sintered body is cooled down to room temperature at an appropriate cooling rate and taken out from the furnace. The lead-based piezoelectric sintered sheet obtained by the present invention had good smoothness, and sufficient peelability between the sheets was obtained. The lead-based piezoelectric sintered sheet element produced by the method of the present invention can be laminated and fired, is highly mass-producible, and can be supplied at low cost. The piezoelectric sintered sheet element thus obtained is useful for applications such as filters, piezoelectric buzzers, pickup elements, and speakers. Examples of the present invention will be described in detail below. Example 1 PbTiO ₃ /PbZrO ₃ = PbTiO 3 /PbZrO 3 with particle size of approximately 1 μm
The binder shown in Table ₁ and 0.5
% by weight of dioctyl phthalate was added to each, and the mixture was thoroughly stirred and mixed with 60% by weight of methyl alcohol based on the calcined raw material, and further mixed for 24 hours in a ball mill to prepare a slurry. This slurry was poured onto a polyester film, formed into a sheet using a doctor blade method, and air-dried to produce a green sheet. Next, using a punching machine, it is punched out into a disc shape with a diameter of 30 mmφ. Particles with a diameter of approximately 5 μm are placed in a parts feeding device (hereinafter referred to as parts feeder) that has a vibration mechanism.
Filled with zirconium oxide powder, the punched green sheet was placed into the apparatus while being heated from the bottom, and the sheet was adhered under the adhesion conditions shown in Table 1. The zirconium oxide powder adheres to the raw sheet that has been put in due to vibration and heating. This raw sheet was laminated into 10 layers, placed on a 99.5% alumina substrate, placed in a furnace, and after first removing organic components, main firing was performed under the firing conditions shown in Table 1. After firing, it was slowly cooled to room temperature and the sintered body was taken out. This sheet has a diameter of 10 to 20% compared to the raw sheet.
% shrinkage, but did not exhibit cracking, warping, perforation, or puncture, and had excellent smoothness. As a result of X-ray analysis, the thus obtained sheet was found to be Pb(TiZr)O ₃ based porcelain having a perovskite structure, and its electrical properties are shown in Table 1. For comparison, Table 1 shows the characteristics of a sintered sheet prepared by a conventional method in which zirconium oxide powder is not attached by vibration or heating. When stacking and sintering was performed using the conventional method, fusion was observed between the sheets due to partial reactions, and sintered sheets could not be obtained in a perfect shape.

[Table] Example 2 PbTiO ₃ :PbZrO ₃ with particle size of approximately 0.5 μm;
Pb(Mg・Nb・Ti・Zr)O ₃ based calcining raw material with a composition ratio of Pb(Mg1/3・Nb2/3)O ₃ = 37.5; 25.0; 37.5 and a binder as shown in Table 2. and 0.5% by weight of dibutyl phthalate were added, and the mixture was thoroughly stirred and mixed with 60% by weight of ethyl alcohol based on the calcined raw material, and further mixed for 48 hours in a ball mill to prepare a slurry. Thereafter, a green sheet was prepared according to the same procedure as in Example 1, and a sintered sheet was obtained in the same manner as in Example 1 under the adhesion and firing conditions shown in Table 2. Table 2 shows various properties of the sintered sheet thus obtained. For comparison, Table 2 also shows the electrical properties of sintered sheets produced by the conventional method in the same way as Table 1, but warpage and fusion were observed in the conventional method. In contrast, with the method of the present invention, a smooth sintered sheet without cracks, warping, perforations, fusions, etc. was obtained.

[Table] As described above, according to the method of the present invention, a high-density and smooth piezoelectric sheet can be obtained.

Claims (1)

[Claims] 1 A piezoelectric material containing lead is kneaded with organic components such as a binder, a plasticizer, and a solvent, and this kneaded material is spread to a certain thickness to create a green sheet, which is punched into any shape. After that, aluminum oxide,
A sintered sheet characterized by heating and vibrating a powder made of at least one of magnesium oxide or zirconium oxide to adhere the powder to the surface of the green sheet, and then stacking and firing the powder. manufacturing method.