JPS6231512B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a sintering method for producing lead-based piezoelectric material, and more specifically, it relates to a sintering method for producing a lead-based piezoelectric material, and more specifically, it sinters a green sheet made of lead-based piezoelectric material to produce a high-density, highly homogeneous sheet. The present invention relates to a method for sintering a lead-based piezoelectric material to obtain a sheet-like piezoelectric element with excellent smoothness. Recently, ceramic piezoelectric elements have been applied to a wide variety of fields, and their density and miniaturization are rapidly progressing. Conventionally, ceramic piezoelectric elements of a predetermined shape depending on the application were manufactured by machining such as cutting a sintered body or a single crystal ingot and then polishing it. There have been problems in that the electrical characteristics of the piezoelectric element deteriorate due to the influence of processing strain, and the processing cost increases. Therefore, from the viewpoint of simplifying the manufacturing process and improving productivity, it has been desired that a piezoelectric element having a desired shape can be completed at the same time as the piezoelectric material is sintered. One way to meet these demands is to knead piezoelectric materials with binders, plasticizers, solvents, etc., and then spread the mixture to a certain thickness to create a green sheet. A manufacturing method is known in which the material is punched into a predetermined shape and then fired. However, in the case of this manufacturing method, deformation due to shrinkage during firing occurs in the sintered sheet product after firing.
There are problems in that cracks, warpage, perforations, pores, and even compositional inhomogeneity occur, and these have a significant effect on mechanical and electrical properties. In order to obtain a piezoelectric sintered compact sheet with high performance and high precision, it is necessary to make the density of the raw sheet as high and uniform as possible.
It is necessary to sufficiently knead the piezoelectric material with the binder, plasticizer, and solvent to improve the dispersion of the sintered material. Furthermore, important conditions include having uniform thickness, high flexibility, easy punching, and no residual processing distortion. In addition, in lead-based voltage body materials, the main component, lead oxide, begins to evaporate at around 800°C, so unless the temperature, atmosphere, packaging method, etc. of the firing process are carefully considered, the piezoelectric properties will deteriorate. In particular, in the case of sheet-shaped piezoelectric ceramic raw materials, the surface area is large compared to the volume, so the evaporation rate of lead oxide is high, making it impossible to sinter the sheet-shaped piezoelectric ceramic raw materials in the atmosphere. be. One way to suppress the evaporation of lead oxide is to sinter the sheet-shaped piezoelectric ceramic raw material in a lead evaporation atmosphere, but keeping the sheet-shaped piezoelectric ceramic raw material in a sealed state is undesirable from the viewpoint of manufacturing costs. , and there are also problems such as a decrease in piezoelectric properties due to the influence of lead vapor. The purpose of this invention is to solve these problems by placing a green sheet of lead-based piezoelectric material with high density and good smoothness on a base plate made of a material that does not easily react with lead at high temperatures. A method for firing a lead-based piezoelectric material, which is characterized by laminating a bed plate on which raw sheets are placed in multiple stages via a spacer that also serves as an airtight holder, and firing the raw sheets in a box-like state. The goal is to provide the following. Next, a green sheet of piezoelectric material sintered by the firing method of the present invention will be described. 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 ternary-component type consisting of a perovskite type compound or a tungsten bronze type compound. Examples of the organic binder include polyvinyl butyral, polyvinyl alcohol, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, methyl cellulose, and ethyl cellulose, but 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. Formability of raw sheet
The processability is better as the amount of both the binder and the plasticizer increases, but since a high-density sheet cannot be obtained when a sintered body is produced, it is necessary to determine the processability by taking into consideration the balance between the two. The optimum amount is 1 to 5% by weight, and the solvent is preferably alcohol, or an ether or ester of polyhydric alcohol. These piezoelectric ceramic materials,
Create a slurry with a binder, plasticizer and solvent;
Pour this slurry onto a smooth substrate such as an organic film and use the doctor blade method to
Form into a sheet with a constant thickness of 2.0 mm and dry to create a smooth raw sheet. The green sheet may also be produced using other methods, such as extrusion or roll rolling. Next, the packaging method, which is a major part of the sintering method of the present invention, will be explained based on the drawings. Figure 1 shows a method for sintering a disc-shaped piezoelectric raw sheet, which has a purity of 98% or more and a porosity that has the least reactivity with lead and does not affect piezoelectric properties.
A piezoelectric raw sheet 2 punched into a disk shape is placed on a flat plate 1 made of 0.5% or less magnesium oxide and having good smoothness. Next, ring spacer 3
is placed on the base plate 1 so as not to contact the piezoelectric raw sheet 2, and the upper base plate 1' is supported by this ring-shaped spacer. This ring-shaped spacer is also made of the same material as the floor plate mentioned above, that is, it has a purity of 98% or more and a porosity of 98% or more.
It may be made of less than 0.5% magnesium oxide, or it may be made of aluminum oxide since it does not come into direct contact with the piezoelectric green sheet. The device shown in FIG. 2 is for sintering a ring-shaped piezoelectric raw sheet, and the purposes of use and the constituent materials of the bottom plates 1, 1' and the spacer 2 are as follows.
Although it is the same as those mentioned above, since the shape of the piezoelectric sheet to be fired is ring-shaped, the internal space becomes large, which may cause evaporation of lead oxide and deformation or warping of the piezoelectric sheet. . For this purpose, the volume of the space is reduced using a disc-shaped spacer 3'. This disc-shaped spacer 3'
has the same thickness as the ring-shaped spacer 2, and has an outer diameter such that the inner diameter part of the ring-shaped piezoelectric sheet does not come into contact with the disk-shaped spacer 3' even if the ring-shaped piezoelectric sheet shrinks due to sintering. The dimensions are as follows. This reduces the volume of the space and improves airtightness. In the two embodiments described above, the reason why the spacer and the bottom plate are not integrated and are made into separate bodies is that the organic components such as the binder and dispersant contained in the piezoelectric raw sheet are removed. This is to prevent the inside from becoming a reducing atmosphere during firing by allowing a slight amount of air to circulate. Next, an example of the piezoelectric raw sheet firing method of the present invention will be described. 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, use a plate punching machine to punch out a disc shape with a diameter of 50 mmφ.
Fill the container using the filling method shown in the figure and place it in the furnace. Main firing was performed under the firing conditions shown in Table 1, and after firing, the sintered body was slowly cooled to room temperature and taken out. This sheet is 10 to 20% more radial than the raw sheet.
It exhibited excellent smoothness without cracking, warping, perforation, or reaction with the floorboard.
As a result of X-ray diffraction, the thus obtained sheet was confirmed to be Pb(TiZr)O ₃ -based porcelain having a perovskite structure. Its piezoelectric properties are shown in Table 1.

[Table] Example 2 PbTiO ₃ ; PbZrO ₃ with particle size of approximately 0.5 μm:
Pb (Mg, Nb, Ti, Zr) O ₃ based calcined raw material with a composition ratio of Pb (Mg _1/3 Nb _2/3 ) O ₃ = 37.5; 25.0; 37.5 is bonded as shown in Table 2. and 0.5% by weight of dibutyl phthalate were added to the calcined raw materials, 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. Below, in the same manner as <Example 1>, the second
A sintered sheet was obtained under the firing conditions shown in the table. Table 2 shows various properties of the sintered sheet thus obtained.

[Table] Example 3 PbTiO 3 ; PbZrO ₃ ; PbTiO ₃ with particle size of approximately 0.5 μm;
2.0% by weight of polyvinyl butyral and 1.5% by weight of Pb(Mg, Nb, Ti, Zr)O ₃ based calcined raw material with a composition of Pb(Mg _1/3 Nb _2/3 )O ₃ = 37.5; 25; 37.5 % of dibutyl phthalate were respectively added, methyl alcohol was added in an amount of 35% by weight based on the calcined raw material, and the mixture was thoroughly stirred and mixed. Further, the mixture was mixed in a ball mill for 24 hours to prepare a slurry. This raw sheet has an outer diameter of 55mmφ,
Punch out a ring shape with an inner diameter of 40mmφ using the method shown in Figure 1.
A sintered body sheet was produced by holding at 1300°C for 2 hours.
The shrinkage rate in this case was found to be 22%. Therefore, the diameter of the disk-shaped spacer shown in FIG. 2 was set to 3.3 mmφ, and the spacer was fired using the casing method shown in FIG. The piezoelectric properties of the obtained sintered ring are shown in Table 3.

[Table] As described above, the present invention has the following excellent effects. (1) By filling the space formed by the spacer and the bottom plate with raw sheets, an airtight structure is created and sintering can be performed without any load being applied from above, resulting in a dramatic improvement in sintering performance and lead oxide A lead-based piezoelectric sintered sheet with high density, high homogeneity, and excellent smoothness can be obtained by suppressing evaporation of
Since it can be fired in multiple layers, productivity is high and manufacturing costs can be reduced, resulting in very large industrial effects. (2) Since the lower bottom plate is made of magnesium oxide and the spacer is made of a material that does not easily react with lead, such as magnesium oxide or aluminum oxide, even if the composition of the piezoelectric green sheet changes, the materials of the upper and lower bottom plates and spacer can be changed each time. No need to consider.

[Brief explanation of the drawing]

The drawings are diagrams for explaining the packaging method used in the sintering method of the present invention, and FIG. 1 is a diagram showing the packaging state when a disc-shaped piezoelectric green sheet is sintered. Here, A is a longitudinal cross-sectional view and B is a cross-sectional view. FIG. 2 is a diagram showing a state in which a ring-shaped piezoelectric green sheet is packed in a box when sintered.
B is a longitudinal cross-sectional view, and B is a cross-sectional view. 1, 1'...Shield plate, 2...Piezoelectric raw sheet,
3, 3'...Spacer.

Claims (1)

[Claims] 1 A piezoelectric material containing lead is mixed with organic components such as a binder, a plasticizer, and a solvent, and the resulting kneaded material is spread to a certain thickness to produce a piezoelectric material. After creating a body sheet and punching it into any shape,
This piezoelectric raw sheet of any shape is placed on a smooth magnesium oxide bottom plate, and by placing the magnesium oxide bottom plate on top of the magnesium oxide or aluminum oxide spacer that also serves as an airtight holder, the upper bottom plate and A method for sintering a lead-based piezoelectric material, which is characterized by firing in an airtight atmosphere without direct contact with a spacer. 2. In the method for sintering a lead-based piezoelectric material according to claim 1, at least one of polyvinyl acetate and polyvinyl butyral is used as a binder in an amount of 0.5 to 5.0% by weight based on the piezoelectric material. A method for sintering a lead-based piezoelectric material comprising: 3. In the method for sintering a lead-based piezoelectric material described in claim 1, the bottom plate has a purity of 98%.
The spacer is made of magnesium oxide porcelain with a porosity of 0.5% or less, and the spacer is made of magnesium oxide porcelain or aluminum oxide porcelain with a purity of 98% or more and a porosity of 0.5% or less. A method for sintering lead-based piezoelectric materials. 4. In the method for sintering a lead-based piezoelectric material according to claim 1, when the piezoelectric green sheet to be sintered has a ring shape, the piezoelectric green sheet is also formed within the inner diameter of the piezoelectric green sheet. 1. A method for sintering a lead-based piezoelectric material, characterized in that a spacer is interposed without contacting the lead-based piezoelectric material, and the dimensions are such that no contact occurs even when the shape of the raw piezoelectric sheet changes during sintering. 5. In the method for sintering a lead-based piezoelectric material according to claim 1, the firing temperature is set to 1150 to 1350.
A method for sintering a lead-based piezoelectric material, characterized by sintering the lead-based piezoelectric material at ℃.