JPH04325465A - Method for burning piezoelectric ceramics - Google Patents

Abstract

PURPOSE:To offer a burning method for obtaining thin sheet-shaped piezoelectric ceramics of stable quality by which a thin sheet-shaped piezoelectric ceramics sintered body obtd. by laminating piezoelectric ceramics and sheet shaped bottom boards and executing burning is excellent in smoothness, free from deformation and deposition, small in the dispersion of shrinkage percentage and free from the deterioration in density. CONSTITUTION:This is a method of laminating plural piezoelectric ceramics green compacts 1 and sheet-shaped bottom boards 2 on a bottom board (setter) for burning and executing burning and is a burning method for piezoelectric ceramics in which, at the spaces between the principal planes of a ringed thin sheet-shaped piezoelectric ceramics green compacts, sheet-shaped bottom boards constituted of the same composition as that of the above piezoelectric ceramics green compacts and furthermore obtd. by adding 3 to 15wt.% zirconia ceramics powder to the above composition are arranged, and burning is executed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing piezoelectric ceramics, and more particularly to a method for firing a plurality of thin plate-shaped piezoelectric ceramic molded bodies containing PbO stacked one on top of the other.

0002

2. Description of the Related Art Piezoelectric ceramics are used in a wide range of applications such as ultrasonic vibrators, actuators, ultrasonic motors, ceramic filters, and buzzers. In recent years, thin plate-shaped piezoelectric ceramics have been used as a base for products such as ultrasonic motor elements and actuator elements.
The number of fields in which it is used is increasing. The method for producing the thin plate-like piezoelectric ceramics is, for example, using sheet molding technology, extrusion molding technology, or a thin-material molding machine to form a thin plate-like piezoelectric ceramic molded body of a predetermined shape into alumina (Al).
2O3), zirconia (ZrO2) or magnesia (M
There is a method in which piezoelectric ceramic molded bodies are placed directly on a ceramic base plate containing gO as a main component and fired, or a method in which a plurality of piezoelectric ceramic molded bodies are stacked on the ceramic base plate and fired. To explain the latter method in more detail, when a plurality of piezoelectric ceramic molded bodies are stacked and fired, in order to prevent the piezoelectric ceramic molded bodies from welding together during the firing process, there is usually a space between the piezoelectric ceramic molded bodies. For example, a method is used in which zirconia ceramic powder having a particle size of about 60 to 100 μm is sprinkled as a bedding powder and then fired. In the case of thin plate-shaped piezoelectric ceramics, the piezoelectric ceramics may be deformed due to the adverse effects of the bedding powder, causing problems. For this purpose, it is necessary to make the piezoelectric ceramic molded body thicker than the desired thickness in advance, and after firing, polish and process both sides of the piezoelectric ceramic sintered body to a predetermined thickness, resulting in high manufacturing costs and poor quality. bad. In addition, the reaction between the zirconia ceramic powder and the components (composition) of the piezoelectric ceramic molded body progresses to some extent, and the shrinkage of the piezoelectric ceramic molded body during the firing process is not achieved smoothly and uniformly. Significant variations occur in the shrinkage rates of individual sintered bodies, and the zirconia ceramic powder can also be a factor in deformation. This tendency is particularly strong in ring-shaped thin plate piezoelectric ceramics.

[0003] In order to improve the drawbacks of the above-mentioned zirconia ceramic powder, for example, a sheet-like base plate containing alumina (Al2O3), zirconia (ZrO2), or magnesia (MgO) as a main component is placed between each piezoelectric ceramic molded body. There is also a method of arranging and firing the piezoelectric ceramic sintered body, but in this case, although deformation such as unevenness of the piezoelectric ceramic sintered body is eliminated to some extent, it is not possible to reduce variations in deformation or shrinkage rate.

0004

[Problems to be Solved by the Invention] As a result of various studies, the present invention has found a means to eliminate such conventional drawbacks, and it is an object of the present invention to provide a piezoelectric ceramic sintered body with almost no deformation and smoothness after firing. It is an object of the present invention to provide a firing method suitable for obtaining stable quality thin plate-shaped piezoelectric ceramics with excellent and extremely small variation in shrinkage rate and good density of piezoelectric ceramic sintered bodies.

[0005]

[Means for Solving the Problems] That is, the present invention provides a method for stacking and firing a plurality of thin plate-like piezoelectric ceramic molded bodies, in which a layer having the same composition as the piezoelectric ceramic molded body is placed between the main surfaces of the piezoelectric ceramic molded body. 3 to 15% by weight of zirconia ceramic powder based on the composition.
This is a method of firing piezoelectric ceramics characterized by arranging and firing a sheet-like base plate containing additives.

[0006]

[Operation] When laminating and firing a plurality of ring-shaped thin plate-shaped piezoelectric ceramic molded bodies, if Al2O3, ZrO2 or MgO powder is scattered between the thin plate-shaped piezoelectric ceramic molded bodies, fine powder will not be dispersed. Various defects occur due to the unevenness of the temperature. As mentioned above, unevenness and deformation occur on the surface of the thin plate-shaped piezoelectric ceramic sintered body due to the penetration of coarse particles of bedding powder and uneven distribution of fine powder, causing problems. For this purpose, as shown in FIG. 1, a sheet-like base plate 2 made of the same composition as the piezoelectric ceramic molded body and made by adding 3 to 15% by weight of zirconia ceramic powder to this composition is used as the piezoelectric ceramic molded body. By stacking a plurality of layers on a firing plate (setter) 3 and firing them, the sintered body is prevented from deformation, cracking, etc.

[0007]

[Examples] Examples of the present invention will be described in detail below while comparing them with comparative examples. Pb [(Mn1/3Sb2/3)0.09Z
A ternary system of r0.46Ti0.45]O3 was selected. Initial starting materials PbO, ZrO with chemical purity of over 99%
2. TiO2, MnO, and Sb2O3 were accurately weighed and mixed to a predetermined mixing ratio, and then pre-sintered at 850 to 900°C. The pre-calcined powder is pulverized using a ball mill, and an appropriate amount of an organic binder, plasticizer, etc. is added to the powder and kneaded.
After producing a green sheet with a thickness of 0.5 mm using the extrusion molding method, it is punched out to have an outer diameter of 45 mm and an inner diameter of φ.
A 25 mm ring-shaped thin plate piezoelectric ceramic molded body was obtained. Next, a method for manufacturing a sheet-like bottom plate to be placed between the main surfaces of each of the molded bodies will be described. The starting materials were precisely weighed so that the composition was the same as that of the piezoelectric ceramic compact. The starting materials used were the same as those used for the piezoelectric ceramic molded body. After mixing these raw materials, they were pre-fired at 850 to 900°C. Next, a predetermined amount of zirconia ceramic powder is accurately weighed and added to the calcined ingredients so that the predetermined amount is added.
Mixed and ground using a ball mill. Zirconia ceramic powder is made by adding a predetermined amount of Y2O3 to a ZrO2 raw material with a chemical purity of 99% or more, and after mixing it has a
Temporarily calcined at ℃ for several hours, crushed and classified using a crusher to obtain a particle size of
The one adjusted to about 0 to 100 μm was used. An appropriate amount of organic binder was added to the powder obtained by mixing and pulverizing as described above, and the mixture was granulated, followed by pressure molding at a pressure of 1.5 t/cm 2 and firing at a temperature of 1230 to 1260° C. for several hours. The obtained sintered body has an outer diameter of 50 mm, an inner diameter of 30 mm, and a thickness of 0.
．． It was finished by cutting and polishing into a shape of 3 mm, and this was used as a sheet-like floor plate to be placed between the main surfaces of the thin piezoelectric ceramic molded body.

Next, as shown in FIG. 1, the ring-shaped thin plate-shaped piezoelectric ceramic molded bodies produced in the above manner were each sandwiched with a sheet-like bottom plate 2 between the main surfaces of the ring-shaped thin plate-shaped piezoelectric ceramic molded bodies 1. 1200 ~ 123
It was baked for several hours at a temperature of 0°C.

[0009] Outer diameter φ5 of Al2O3, ZrO2, MgO
0mm, inner diameter φ30mm, thickness 0.3mm sheet-like bottom plate and piezoelectric ceramic molded body (setter) for firing.
We loaded the piezoelectric ceramics into a furnace and fired them to see how the thin plate-shaped fired piezoelectric ceramics were made. The results are shown in Tables 1 and 2.

[Table 1]

[Table 2]

[0010] Tables 1 and 2 show Comparative Example 1 in which an Al2O3 sheet bottom plate was made using conventional Al2O3 powder, and Comparative Example 2 in which a ZrO2 sheet bottom plate was made using conventional ZrO2 powder. and conventional MgO
Comparative Example 3: Making an MgO-based sheet-like floor plate using powder
These sheets of Al2O3, ZrO2, and MgO were sandwiched between thin piezoelectric ceramic plates, laminated, and fired, and the finished piezoelectric ceramic fired body was checked to determine whether it passed or failed. The finished state of the fired piezoelectric ceramic body is determined by the density of the fired piezoelectric ceramic body after firing,
Conditions such as shrinkage rate, variation in shrinkage rate, change in dimensions after firing, warpage, and durability are observed. Durability in Table 2 (
(Refer to the durability in Table 4), the durability cannot be seen just by firing once, so here we will repeat firing 8 times at the prescribed firing temperature to reduce the reactivity between the piezoelectric ceramics and the sheet-like base plate, i.e., welding, deformation, etc. Check for cracks, welding, deformation, etc.
Items with no cracks were marked with an ○ mark to pass, and items with any of the following, such as welding, deformation, or cracks, were marked with an x mark as a failure. In addition, as shown in Fig. 2, AA of the ring-shaped thin plate piezoelectric ceramic after sintering shows a change in external dimension, and A'A
´ is the outer diameter dimension perpendicular to the outer diameter dimension of AA, BB
indicates the change in the inner diameter dimension, and B'B' indicates the inner diameter dimension in the direction perpendicular to the inner diameter dimension of BB. From Tables 1 and 2, alumina (Al2O3), zirconia (ZrO2),
Comparing each magnesia (MgO) sheet-like board,
A sheet-like base plate of zirconia (ZrO2) is made of alumina (A
12O3) and magnesia (MgO).

Pb [(M
n1/3Sb2/3)0.09Zr0.46Ti0.4
5] The amount of zirconia (ZrO2) powder added to O3 is 0 or 2.
, 3, 5, 10, 15, 20, 30% by weight,
Sample numbers 1, 2, 3, 4, 5, 6, 7, 8 respectively
In the same manner as in Comparative Examples 1, 2, and 3, the density, shrinkage rate, variation in shrinkage rate, dimensional change, warping, durability, etc. of the ring-shaped thin piezoelectric ceramic fired body were evaluated. I looked at the characteristics. The results are shown in Tables 3 and 4.

[Table 3]

[Table 4]

Tables 3 and 4 show that the basic compositions A to F of the sheet-like floor plate compositions are the same as the composition of the piezoelectric ceramics, and Pb
[(Mn1/3Sb2/3)0.09Zr0.46Ti
0.45] It has a composition consisting of the chemical formula of O3, and various zirconia (ZrO2) powders are added to this composition,
The samples are represented by sample numbers 1 to 8, and the same characteristics as Comparative Examples 1, 2, and 3 were measured to show the results of examining sheet-like floor plates that have less negative impact on the fired piezoelectric ceramic body after firing. . As a result, sheet-like floor plates containing zirconia ceramic powder in an amount of 3% to 15% by weight passed the durability test. When used as a sheet-like base plate with a composition in which the amount of zirconia ceramic powder added is less than 3% by weight, repeated firing causes a reaction between the sheet-like base plate and the piezoelectric ceramic sintered body, resulting in welding. Again 1
When the amount exceeds 5% by weight, density decreases and shrinkage rate decreases. Therefore, the compactness of the piezoelectric ceramic sintered body is lost, resulting in poor quality. Furthermore, the variation in shrinkage rate and the change in dimensions become larger, and therefore the maximum value of warpage becomes larger. Since the mechanical strength of the sheet floorboard (not shown in Table 3) also decreases, it was found that a range of 3 to 15% by weight is effective. After removing the piezoelectric ceramic sintered bodies at the bottom of each of the six stacked ring-shaped thin plate piezoelectric ceramic sintered bodies 4 obtained, the density of the remaining piezoelectric ceramic sintered bodies, The shrinkage rate, shrinkage rate variation, deformation, warpage, and durability were investigated, and the density was measured by the Archimedes method. The average value of A' was used as the outer diameter dimension, and was determined by a predetermined calculation method. Also, the variation in shrinkage rate is due to the variation in the average value of AA, A'A' (
Standard deviation values) were used for comparison and evaluation. The measurements were performed on n=50 samples for each sample number. The deformations are AA, A'A' and BB, B'B' as shown in Figure 2.
Measure the dimensions of AA/A'A', BB/B'B' (AA
>A'A', BB>B'B') or A'A'/AA, B
While checking Max at 'B'/BB (when A'A'>AA, B'B'>BB),
Comparison and evaluation were made based on the maximum value of warpage in m).

[0013] In Tables 3 and 4, the sample numbers marked with * correspond to the firing method of the present invention.

As is clear from Tables 3 and 4, the ring-shaped thin plate-shaped piezoelectric ceramic obtained by the firing method of the present invention has a high density, shows an appropriate shrinkage rate, and has a high density. However, it is clear that the variation in shrinkage rate and deformation are small, and it is a good piezoelectric ceramic sintered body.

[0015]

Effects of the Invention As described above, in the firing of a plurality of stacked ring-shaped thin plate-like piezoelectric ceramic bodies, the ring-shaped thin plate-shaped piezoelectric This is a method of arranging and firing a sheet-like base plate that has the same basic composition as the ceramic compact (object to be fired) and contains zirconia ceramic powder in an appropriate range, and is different from the conventional material in the comparative example. The present invention has realized a firing method suitable for obtaining a ring-shaped thin plate-shaped piezoelectric ceramic sintered body of good quality, which could not be achieved with a sheet-shaped base plate made of the same material.

[0016] When a composition containing less than 3% by weight of zirconia ceramic powder additive is used as a sheet-like base plate, the resulting ring-shaped thin plate-like piezoelectric ceramic sintered body is good at the initial stage, but cannot be used repeatedly. In this case, it may react with the sheet-like floor plate and weld, which is undesirable.
If the amount exceeds 5% by weight, the density and shrinkage rate of the resulting ring-shaped thin plate piezoelectric ceramic sintered body will decrease, and the piezoelectric ceramic sintered body will lose its original tightness and shrink. This method is excluded from the scope of the present invention because it causes inconveniences such as increased deformation such as variation in ratio, change in dimensions, and warping, and furthermore, a decrease in the mechanical strength of the sheet-like floorboard itself.

In the embodiments of the present invention, a method for firing ring-shaped thin plate-shaped piezoelectric ceramics has been described, but according to the present invention, thin plate-shaped disc-shaped and square plate-shaped piezoelectric ceramics are also investigated at the same time. Its improvement effect has been confirmed. As described in detail above, the firing method of the present invention can be applied to a wide range of applications, particularly to thin plate-shaped piezoelectric ceramics, and is of great industrial value.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment used to explain a firing method in an embodiment of the present invention.

FIG. 2 is a plan view of an example of a ring-shaped thin plate-shaped piezoelectric ceramic sintered body, which was also used to explain measurement and evaluation.

[Explanation of symbols]

1 Piezoelectric ceramic molded body 2 Sheet-like floorboard 3. Baking plate (setter) 4 Piezoelectric ceramic sintered body

Claims (1)

[Claims] 1. In a method of stacking and firing a plurality of thin plate-like piezoelectric ceramic molded bodies, the piezoelectric ceramic molded body is made of the same composition as the piezoelectric ceramic molded body, and the composition is A method for firing piezoelectric ceramics, which comprises arranging and firing a sheet-like base plate containing 3 to 15% by weight of zirconia ceramic powder.