JPS6241753A - Perovskite ceramic and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to perovskite ceramics having a high dielectric constant and low temperature dependence and electric field dependence, and a method for producing the same, and in particular perovskite ceramics having small crystal grain size and small variations thereof. Concerning porcelain and its manufacturing method.

[Prior Art] Dielectric materials for ceramic capacitors are required to have a high dielectric constant and low dependence on temperature and electric field. However, a high dielectric constant and a reduction in dependence on these are contradictory demands, and conventionally it has been difficult to satisfy them at the same time. As a solution to this problem, the present inventors proposed a mixed sintered porcelain in which two or more types of perovskite porcelain materials with different Curie temperatures, which exhibit high dielectric constants, are mixed together and a method for manufacturing the same (
(Japanese Patent Application No. 59-182702), this porcelain is made by the process shown in FIG. That is, for example, Pb(Feh town/
3), (Fed Nby, Koma03 and Pb(F
"Ys"/) ) o, r; (Feg Nb J,, g
After weighing, mixing, pre-calcining and crushing 03,
The two types of perovskites are mixed and unfired so that the two types of perovskites do not completely form a solid solution. The porcelain obtained in this way: does not require any subcomponents to improve the above-mentioned dependence like conventional porcelain, and has a high dielectric constant of more than 10,000 yen, while also improving its temperature dependence and electric field dependence. This can be reduced to about 172 compared to the conventional value. ■Dependency can be freely controlled by combining the porcelain materials to be mixed and their mixing ratio. It has the following characteristics. However, the perovskite-based porcelain materials to be mixed have different grain growth rates during main firing, making it difficult to form uniform crystal grains, and those with fast grain growth rates have grain sizes of up to 10 grains. There was room for.

[Problem to be Solved by the Invention 1] The present invention improves the above-mentioned conventional method so that the crystal grain size is small and
Another object of the present invention is to provide perovskite porcelain with small variation in particle size and a method for producing the same.

[Means for solving the problem] Perovskite is a complex oxide represented by the chemical formula ABO3, where A forms a simple cubic lattice, and B forms an O
is located at the face center position.

-1- In order to achieve the above objectives, in the present invention,
It is an oxide of an element that does not occupy the B position of level B vitreous porcelain Al3O3 when two types of perovskite porcelain materials having 5% of the Curie temperature are mixed and fired without forming a complete solid solution. It has a higher melting point than perovskite porcelain and is characterized by the addition of chemically stable metal oxides.

``Sakukawa] The oxide mentioned in
It is hardly dissolved in the solid porcelain material, and exists mostly at the grain boundaries, and Belovsky!・The crystal grains 1 &ffi are suppressed, and there is almost no change in the dielectric properties.

[Example 1] As an example of the present invention, two types of perovskite-based vessel materials were Pb(Fe, Wy3)x(Fe, Nb
1-%05 (O≦X≦1), using materials with x = 0.1 and materials with We will explain the results in this case.

Raw material powder PBO whose manufacturing process is shown in FIG.

Fe2,03, WO:q, Nbz[15%] were weighed so that the above X was 0.1 and 0.5, respectively, and mixed with pure water in a ball mill. After dehydration and drying, they were calcined in air for one hour at 1050°C and 850°C, respectively, and then ground in a ball mill. For the composition after pre-calcination, 20=20~ using CuKα rays.
The X-ray diffraction pattern in the range of 90'' was measured, and it was confirmed that the material was a predetermined perovskite ceramic material.
By mixing equimolar amounts of different types of perovskite porcelain materials, Dy
20. A was added thereto, and a polyvinyl alcohol solution binder was used to pressure-form the material into a bereft with a diameter of about 1211 mm and a thickness of about 0.71 mm, and main firing was performed in air at 1000° C. for 1 hour. The fired surface of the fired porcelain was examined using an electronic m* mirror (magnification: 1,000
The average grain size of the crystal grains (Martir+diameter)
was measured. In addition, Ag electrodes were baked on both sides of the fired porcelain, and the dielectric properties were measured by changing the dielectric constant εr to −40 at l kHz.
The temperature range was 120°C.

FIG. 2 shows the amount of DyL03 added, the average particle size of porcelain, and mo1% relative to the amount. Also, from Figure 0, in which the number of measured crystal grains was 20, the addition ψ of ayλ03 was 0.
When increasing to 1mol1%, the crystal grain size decreases to 2.6cm, which is about half of the 5.04m without additives, and the particle size deviation also decreases from 1.5 to 10gm compared to the case with no additives. Compared to that, it is considerably smaller at 1 to 4 ru. However, when OI% exceeds 0.2%, the average particle size and particle size deviation become large. Therefore, Dy, 03 is 0. i
Grain growth is inhibited when 1% to 0.2mol1% of o is added.
It can be seen that the effect of , becomes significant.

When another metal ion is substituted at the B position of the perovskite ceramic material (ABO3), the Curie temperature changes,
The peak of the dielectric constant seen in the temperature dependence shifts. However, in the case of no addition of ay, , o3 shown in Fig. 3 (in the figure (
Comparing the dielectric constant and temperature properties of perovskite ceramics when a)) and 0.1mol1% ((b) in the figure) are added, it is found that even if 0.1% of Dyyu03 is added, there is no additive. As in the case of , weak dielectric constant peaks occur at 20℃ and 80℃,
I can't see any peak movement, and D! The addition of z03 does not impair the flattening of the dielectric constant and its temperature dependence. Therefore, the added Dy2O3 is diffused into the crystal grains of the perovskite ceramic material with X=O,l and x=0.5. It is thought that it exists mainly at grain boundaries rather than at grain boundaries, and only exerts the effect of suppressing grain growth.

This example describes a method of pre-firing and pulverizing each of the porcelain materials to be mixed, and then simultaneously adding a metal oxide (for example, Dy4Ch) that suppresses grain growth when mixing to a desired molar ratio, and then firing. As explained above, as shown in Fig. 4, when weighing the raw material powder, a metal oxide (for example, ay2o3) that inhibits grain growth is added at the same time, and calcined and pulverized to achieve the desired molar ratio. Even if they are mixed and fired, the effect remains the same. Furthermore, in this case, only the perovskite with a faster grain formation p speed (x = 0.5 in this example) during main firing has grains! A similar effect can be obtained simply by adding a metal oxide that suppresses the & length.

The oxide to be added must not form a solid solution in the perovskite porcelain during firing, and in particular must be an oxide of a metal element that does not replace the atom at the B position (body center position) in the general formula represented by ABO3. This is necessary in order not to damage the dielectric properties of the material. Furthermore, the fact that the oxide is hardly dissolved in solid solution in the provskite and is present at the grain boundaries is effective for suppressing the growth of the crystal grains. For this purpose, chemically stable oxides that have a higher melting point than perovskite porcelain are effective. Examples of such oxides include Fly,03 (melting point 2375°C) and GdJ3 (melting point 239°C).
5''C) and SmbO* (melting point 2250°C) also exhibit similar effects.

The method shown in Figure 1 differs from the conventional method shown in Figure 5 in that a metal oxide (for example, Dy1O3) is added to suppress the growth of crystal grains when mixing the pre-fired porcelain material. The method shown in Figure 4 is basically the same as the conventional method, with the only difference being that a metal oxide (for example, DffJh) that suppresses grain growth is added during weighing of the raw material powder. It goes without saying that the method can also be applied to cases where three or more different types of perovskite ceramic materials are mixed and sintered.

[Effect of the invention 1] As explained above, the addition of a metal oxide such as DYzQ3, which suppresses crystal grain growth, improves crystal grain growth without impairing the dielectric properties of porcelain in which two or more types of perovskite ceramic materials are mixed. It has the advantage that the grains can be made smaller and the particle size deviation can also be made smaller. Therefore, when used as a material for a multilayer ceramic capacitor, it has the advantage that the dielectric ceramic layer can be made thinner and defects such as pinholes can be reduced.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the steps of an embodiment of the method for producing perovskite ceramics of the present invention, Figure 2 is a diagram showing the relationship between the addition field of Dy 03 and the Y uniform grain system, and Figure 3 is a diagram showing the addition of Dy2O3. Figure 4 shows the temperature dependence of the permittivity of perovskite porcelain with and without it. Figure 4 shows the manufacturing process of another embodiment of the present invention. Figure 5 shows the conventional manufacturing process of perovskite porcelain. : It is a diagram showing the process.

Claims (1)

[Claims] 1) Two or more chemical formulas ABO_ with different Curie temperatures
In the perovskite porcelain in which the perovskite porcelain material represented by 3 is mixed, B of ABO_3 is
Perovskite-based porcelain, characterized in that it contains a metal oxide that does not occupy a certain position and has a melting point higher than the melting points of the two types of perovskite-based porcelain materials. 2) Two or more chemical formulas ABO_ with different Curie temperatures
The raw material powder of the perovskite porcelain material represented by 3 is calcined separately in advance to obtain two or more types of perovskite porcelain materials having different Curie temperatures, and then these materials are crushed and mixed in an appropriate non-zero ratio. When doing so, the AB
Adding an oxide of a metal element that does not occupy the B position in O_3 and having a melting point higher than the melting point of the two or more types of perovskite ceramic materials, completely melting the two or more types of perovskite ceramic materials. A method for manufacturing perovskite mixed sintered porcelain, which is characterized by sintering without forming a solid solution in perovskite. 3) Two or more chemical formulas ABO_ with different Curie temperatures
At least one kind of the raw material powder of the perovskite ceramic material represented by 3 is an oxide of a metal element that does not occupy the B position of the above ABO_3, and has a melting point higher than the melting point of the two or more kinds of perovskite ceramic materials. After adding the material, pre-calcining them separately to produce two products with different Curie temperatures.
A method for producing perovskite porcelain, which is characterized in that after producing more than one type of perovskite porcelain materials, the materials are pulverized and mixed in an appropriate non-zero ratio, and sintered without forming a complete solid solution.