JPH05182521A - Manufacture of bzt sintered body - Google Patents

Abstract

PURPOSE:To heighten the degree of sintering so as to simply manufacture of a BZT sintered body of high density with a high yield, without no axially about characteristic deterioration, by baking calcined substance expressed by means of Ba3ZnTa2O9 after adding ZnTa2O6 thereto. CONSTITUTION:The powder of calcined substance expressed by Ba3ZnTa2O9, being main material, and the powder of ZnTa2O6 are mixed together sufficiently in pure water of approximately 1.5 times by weight ratio and are dried in the air thereafter. Then, adequate amount of organic binder is added to the dried mixed powder so as to be molded by a metal mold, and thereafter a molded body is baked. In this case, normally the range from 0.01 to 2 percentage by weight of, desirably the range from 0.01 to 0.8 percentage by weight of ZnTa2O6 is added to normally 100 percentage by weight of calcined substance of Ba3ZnTa2O9. Since the degree of sintering is heightened thereby, it is possible to obtain a BZT sintered body of high density with a high yield, to maintain excellent characteristic, which the BZT possesses by nature, and to manufacture the sintered body simply with the high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a BZT sintered body used for a high frequency dielectric resonator or the like.

[0002]

2. Description of the Related Art A dielectric material having a high dielectric constant and a high Q value in a microwave region of 1 GHz or more is called a high frequency dielectric, and researches for improving the performance of this high frequency dielectric are actively conducted. .. As a result, a high frequency dielectric having excellent characteristics has been found.

Among them, ceramics having a perovskite type crystal structure represented by the composition formula of A ₃ BC ₂ O ₉ are excellent high frequency dielectrics, and are sintered having a perovskite type crystal structure represented by Ba ₃ ZnTa ₂ O _9. The body (BZT sintered body) is also put to practical use. This BZT
Sintered body by molding a powder of calcined product represented by Ba ₃ ZnTa ₂ O ₉ sintered obtained by causing sintering.

[0004]

However, Ba ₃
The powder of the calcined material of ZnTa ₂ O ₉ has low sinterability and it is difficult to obtain a dense BZT sintered body. A BZT sintered body having a low density does not exhibit the high dielectric constant and high Q value characteristics inherent to BZT. Normally, 15 powders of Ba ₃ ZnTa ₂ O ₉ calcined material are used.
Even if it is fired at a firing temperature of 50 ° C. for 4 to 5 hours, the density is at most (theoretical value) 80%. The BZT sintered compact having a high density cannot be manufactured with high yield.

In the case of a ceramic high frequency dielectric, the sinterability is improved by adding a sintering aid to the calcined product. But,
The addition of the sintering aid is certainly effective in improving the sinterability, but from the viewpoint of the basic composition of the ceramic, the presence of impurities makes the other properties significantly superior. It is not preferable in that it does. In view of the above circumstances, it is an object of the present invention to provide a method capable of easily producing a high-density BZT sintered body without disturbing the development of original excellent characteristics and with a high yield. To do.

[0006]

In order to solve the above-mentioned problems, in the method of manufacturing a BZT sintered body according to the present invention, B
ZntA the calcined product represented by a ₃ ZnTa ₂ O _{9 2}
O ₆ is added for firing. Hereinafter, the production of the BZT sintered body according to the present invention will be specifically described.

First, the main material of Ba ₃ ZnTa ₂ O ₉
The process of creating the calcined product represented by the above will be described. The starting materials containing the Ba component, the Zn component and the Ta component are weighed according to the stoichiometric ratio of BZT. As the Ba component, for example, BaCO ₃ powder is used. As the Zn component, for example, ZnO powder is used. As the Ta component, for example, Ta ₂ O ₅ powder is used.

The above starting materials are sufficiently mixed in pure water in a weight ratio several times by a ball mill, and then dried in air. After molding the mixed powder after drying using a mold, the obtained molded body is calcined in air at 800 to 1200 ° C. for 3 to 20 hours and then cooled, and then pulverized using a rotary ball mill. And pulverize it. The powder of the calcined material of Ba ₃ ZnTa ₂ O ₉ usually has an average particle size of about 2 μm or less.

Now, Ba ₃ ZnTa ₂ O which is the main material
The powder of ₉ calcined products will be completed. Next, a process of producing a powder of ZnTa ₂ O ₆ which is a secondary material added to the main material will be described. The starting materials containing the Zn and Ta components are weighed according to the stoichiometric ratio of ZnTa ₂ O ₆ .

As the Zn component, for example, ZnO powder is used. As the Ta component, for example, Ta ₂ O ₅ powder is used. The starting material for preparing ZnTa ₂ O ₆ is thoroughly mixed in pure water at a weight ratio of 2-3 times by a ball mill, and then dried in air. After molding the mixed powder after drying using a mold, the obtained molded body is fired in air at a temperature of about 950 to 1150 ° C. for about 18 to 30 hours and then cooled, and then pulverized by a vibration mill. And pulverize. The powder of ZnTa ₂ O _{6 as} an auxiliary material is usually made to have an average particle size of about 2 μm or less.

With this, Zn as a sub-material added to the main material is
The powder of Ta ₂ O ₆ is completed. Next, steps for obtaining a sintered body using the ceramic powders of the main and auxiliary materials thus obtained will be described. The powder of the calcined product represented by Ba ₃ ZnTa ₂ O ₉ and the powder of ZnTa ₂ O ₆ are sufficiently mixed in pure water having a weight ratio of about 1.5 times using a ball mill, and then dried in air.

An appropriate amount of an organic binder is added to the mixed powder after drying and the mixture is molded with a mold, and then the formed compact is subjected to main firing. The amount of organic binder added is 10 mixed powders.
It is about 0.01 to 0.06 wt% with respect to 0 wt%, and examples of the binder include polyvinyl alcohol and the like. In the main calcination, normally, after heat treatment at 1500 to 1550 ° C. for about 3 to 5 hours, heat treatment for annealing is performed at a temperature of 1400 to 1450 ° C. for 50 to 120 hours.

Regarding the amount of ZnTa ₂ O ₆ added, Z is usually 100 wt% of Ba ₃ ZnTa ₂ O ₉ calcinated product.
The powder of nTa ₂ O ₆ is usually added in the range of 0.01 to ₂ wt%, preferably 0.8 wt%. More preferably in the range of 0.2-0.4 wt%,
In this range, a Q value exceeding 20,000 can be obtained. 0.
If it is less than 01 wt%, it tends to be difficult to obtain a sufficient addition effect, and if it exceeds 2 wt%, the Q value tends to be insufficient.

The BZT sintered body obtained by the method of the present invention has the following performance. Relative permittivity: around 28.5 ... at 10 GHz Q value: 7000 to 20000 ... at 10 GHz Temperature coefficient of resonance frequency τ _f : around 5 ppm / ° C Density: Approximately 99% ... Perfect sintered body The theoretical density of 100%
To

[0015]

[Action] In the manufacturing method of the BZT sintered body of the present invention, ZntA ₂ O added to the main material serving Ba ₃ ZnTa ₂ O _{9
Since 6} enhances sinterability, a high-density BZT sintered body can be reliably obtained. Ba ₃ ZnTa ₂ which is difficult to sinter as it is
The powder of the calcined product of O ₉ can be obtained as a high-density sintered body with high yield. That is, ZnTa ₂ O ₆ plays a role of a sintering aid.

ZnTa ₂ O having an effect of improving sinterability
₆ is, of course, a compound different from BZT, but since it contains no elements other than the elements contained in BZT, the impurity element is extremely thin and there is virtually no adverse effect on other characteristics.
In the obtained BZT sintered body, the dielectric constant, Q
For the value and the temperature coefficient of the resonance frequency, the proper BZ
It has excellent characteristics that T originally has. For example, a Q value of about 20,000 can be easily obtained. Commercial BZ
The Q value of the T-sinter is usually less than 10,000.

In addition, ZnTa ₂ O ₆ as a sub-material is
Since the same starting material as the main raw material is used to obtain the same step, and after ZnTa ₂ O ₆ is added, the same step as the conventional one is executed, the present invention is extremely easy to carry out. An excellent BZT sintered body can be easily obtained.

[0018]

Embodiments of the present invention will be described below. Needless to say, the present invention is not limited to the following embodiments. - Example 1 First, a powder of calcined product of Ba ₃ ZnTa ₂ O ₉ prepared in the following manner.

BaCO ₃ powder, ZnO powder and Ta ₂ O ₅ powder as starting materials were weighed in accordance with the stoichiometric ratio of BZT and thoroughly mixed in pure water twice in weight ratio with a resin ball mill. Dried in air. After molding the mixed powder after drying using a mold, the molded body is made into 1000
Ba ₃ by calcination in air at ℃ for 18 hours, then cooling, and then pulverizing by a rotary ball mill to powder.
A powder of a calcined product represented by ZnTa ₂ O ₉ was obtained. The average particle size of the obtained powder was about 1 μm.

On the other hand, ZnTa ₂ O ₆ powder was prepared as follows. Starting materials ZnO powder and Ta ₂ O
_{5 The} powder was weighed according to the stoichiometric ratio of ZnTa ₂ O ₆ ,
The mixture was thoroughly mixed in pure water having a weight ratio of 2 using a resin ball mill and then dried in air. After molding the mixed powder after drying using a mold, the molded body is baked in air at 1150 ° C. for 24 hours, cooled, and then pulverized by a vibration mill to obtain ZnTa ₂ O ₆ powder. It was The average particle size of the obtained powder was about 1 μm.

Ba ₃ Zn which is the main material thus obtained
Powder of calcinated material of Ta ₂ O ₉ and ZnTa ₂ O as an auxiliary material
Air ₆ powder is mixed thoroughly with the resin ball mill in pure water 1.5 times by weight ratio by incorporating a ZntA ₂ O ₆ with 0.3 wt% with respect to calcined product 100 wt% Dried in. 0.06 wt% of polyvinyl alcohol, which is an organic binder, is added to the mixed powder after drying and the mixture is molded with a mold, and then the molded body thus prepared is subjected to main firing. The dimensions of the molded body were 14 mm in diameter and 6 mm in height. In the main firing,
A heat treatment for annealing was performed at 1550 ° C. for 5 hours and then at 1400 ° C. for 80 hours to obtain a BZT sintered body.

[0022] - to calcined product 100 wt% of Example _{2- Ba 3 ZnTa 2 O 9,} Zn
A BZT sintered body was obtained in the same manner as in Example 1 except that Ta ₂ O ₆ was added in an amount of 0.5 wt. - to calcined product 100 wt% of Example _{3- Ba 3 ZnTa 2 O 9,} Zn
A BZT sintered body was obtained in the same manner as in Example 1 except that Ta ₂ O ₆ was added in an amount of 0.8 wt.

[0023] - to calcined product 100 wt% of Example _{4- Ba 3 ZnTa 2 O 9,} Zn
A BZT sintered body was obtained in the same manner as in Example 1 except that Ta ₂ O ₆ was added in an amount of 1.0 wt. - except that no addition of powder of Comparative Example 1- ZnTa ₂ O ₆ is Example 1
A BZT sintered body was obtained in the same manner as in.

Regarding the BZT sintered bodies of Examples and Comparative Examples,
The relative permittivity, Q value, temperature coefficient of resonance frequency and density were measured. The measurement results are shown in Table 1. The Q value was measured according to the cylinder resonance method. The measurement frequency is 7 GHz, Q ×
The Q value at 10 GHz was calculated using the relationship of f = constant. Diameter 12 and height 5m from BZT sintered body
A sample of m was obtained to construct a resonator. Pure copper plates (diameter 44 mm, thickness 2 mm) are used for the metal plates that sandwich the resonator under test, and the effective conductivity σe is 80% of the direct current conductivity σo of copper.
(Σe = 0.8 × σo). In addition, the analyzer used for the measurement is 8720 manufactured by Hewlett Packard.
A) was used.

In the case of the cylindrical resonance method, a TE mode dielectric resonator is designed and created based on the dielectric constant of a high frequency dielectric, and the created resonator is sandwiched between copper plates having a diameter of about 4 times the diameter of the network analyzer. To measure the resonance frequency and half width of the resonator. The Q value directly calculated from the measurement value of the network analyzer at this time includes an error due to the loss due to the copper plate. The loss due to the surface resistance of the copper plate is included as an error component.

In order to obtain the Q value of only the high frequency dielectric itself, it is necessary to remove the error caused by the loss in the copper plate. However, if the frequency is as high as 10 GHz, the high-frequency current flows only on the surface of the copper plate, so even if the direct current conductivity σo of copper is applied as it is to calculate the loss in the copper plate, it will not be a correct value, and the microwave region It is necessary to obtain the effective conductivity σe at and apply this. The effective conductivity is obtained by calculating the surface resistance based on the difference between the resonance frequency of the TE ₀₁₁ mode resonator and the TE ₀₁₃ mode resonator made of the same material and the Q value directly obtained by the network analyzer. Effective conductivity σe / DC conductivity of copper σo
Find the ratio of. In this case, this ratio is 0.8. The Q value due to the surface resistance of the copper plate was obtained from the obtained results, and the Q value due to the obtained surface resistance of the copper plate was directly obtained
A correction calculation for subtracting the value is performed to finally obtain the Q value of the BZT sintered body.

[0027]

[Table 1]

As shown in Table 1, according to the present invention, even if the calcined product is not sintered in the comparative example, ZnTa
It is well understood that the addition of ₂ O ₆ makes it possible to easily obtain a BZT sintered body having a sufficient relative permittivity, Q value, temperature coefficient of resonance frequency and density.

[0029]

According to the method for producing a BZT sintered body of the present invention, Zn added to Ba ₃ ZnTa ₂ O ₉ as a main material is added.
Since Ta ₂ O ₆ enhances the sinterability, not only a high-density BZT sintered body can be obtained with a good yield, but ZnTa ₂ O ₆ having the effect of improving the sinterability causes a decrease in the Q value. Such an impure character is extremely thin, and the obtained BZT sintered body has the excellent characteristics originally possessed by proper BZT. Moreover, ZnTa ₂ O ₆ uses the same starting material as the main material and uses the same process. In addition, after the addition of ZnTa ₂ O ₆ is carried out, the same steps as the conventional ones are merely performed, so that an excellent BZT sintered body can be easily obtained.

The amount of ZnTa ₂ O ₆ added is Ba ₃ ZnTa.
If it is 0.01 to ₂ wt% with respect to 100 wt% of the calcined product of ₂ O ₉ , the ZnTa ₂ O ₆ addition effect will surely occur in an appropriate state.

Claims (2)

[Claims] 1. A method of manufacturing a BZT sintered body, which comprises firing a calcined material represented by Ba ₃ ZnTa ₂ O ₉ to sinter, and adding ZnTa ₂ O ₆ to the calcined material and firing. A method for manufacturing a BZT sintered body, comprising: _2. The additive amount of ZnTa ₂ O ₆ is Ba ₃ ZnT.
0.0 per 100 wt% of the calcined product represented by a ₂ O ₉
The method for producing a BZT sintered body according to claim 1, wherein the amount is 1 to 2 wt%.