JPS6054269B2 - dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes barium oxide (BaO), titanium oxide (TI
O0), samarium oxide (Sm.

O0) and bismuth titanate (2Bi. to 3Ti)
This book is about dielectric ceramic compositions for high frequency use composed of components of O2), and its purpose is to improve the dielectric constant
The object of the present invention is to provide a dielectric ceramic having a large ε), stable temperature characteristics, and whose temperature coefficient can be varied over a wide range depending on the application. In recent years, with advances in technology for high-frequency circuits that handle microwaves and millimeter waves (hereinafter collectively referred to as microwaves) with wavelengths of several α or less, efforts are being made to miniaturize these circuits.

Until now, cavity resonators, antennas, etc. have been used in these high-frequency circuits, but the size of these devices is comparable to the wavelength of microwaves, which has been an obstacle to miniaturization.

In order to solve this problem, a method has been used to shorten the wavelength itself by using dielectric ceramics with a high dielectric constant. TiO is a material suitable for such applications.
2-based materials are often used, such as TiO2-ZrO
21 sno2 system, CaTiOa-MgTiO3-Ll2
Oa-liver iO2 system, recently Ba (Znll mound a21
3) 0. -Ba(ZnlI3Nb213)O, and other dielectric ceramics are known. However, when dielectric porcelain is made from these materials, the dielectric constant is 30 to 4.
For example, the resonance frequency is about 11 GH2 (
7) In the case of an X-band dielectric resonator, if a material of ■30 is used for E, it will be a small unit with a diameter of 5.6 Tfn and a thickness of about 2.2 mm, but the frequency will drop and the u-band of about 2 GH2 will be produced. When using the same material E as in 30, the diameter is 30.7 wglt and the thickness is about 12.3 wm, which makes the shape significantly larger. If the dielectric constant of the material used here increases to 8 degrees, the size can be reduced to about 18.8 Twt in diameter and 7.5 Tnm in thickness, but conventional materials meet such requirements. I couldn't satisfy you. The present invention has been made to solve the above problems, and aims to provide dielectric porcelain that has a large dielectric constant, stable temperature characteristics, and whose temperature coefficient can be varied over a wide range depending on the application. That is. The inventors conducted various studies on materials that satisfy the above requirements, and found that in the composition represented by XBaO-YTiO2-ZSm2O3, 5≦x≦23 (mol%), 57≦y≦82.
．． 5 (mol%), 2.5≦z≦37.5 (mol%), x
Porcelain with a composition in which 2Bi203/3Ti02 is added to the main component in the range of +y+z=100 (mol%) in an amount not exceeding 10% by weight of the total amount is an excellent dielectric porcelain for high frequency use. I discovered that.

To explain the reason for limiting the range of the main component composition, BaO
If the amount X exceeds 23 mol%, the TiO2 amount y is less than 57 mol%, or the Sml2O3 amount y becomes less than 2.5 mol%, it becomes difficult to sinter the porcelain, and the no-load Q decreases, making measurement impossible. It is.

Furthermore, if x is less than 5 mol% or z exceeds 37.5 mol%, the sintering of the porcelain will become unstable and the no-load Q will decrease, making measurement impossible, and if y exceeds 82.5 mol%. This method is excluded from the scope of the present invention because the sintering of the porcelain becomes unstable and the temperature characteristics change significantly.
Regarding the addition of the subcomponent 2B1203/3Ti02,
As the additive amount increases, the dielectric constant can be increased and the temperature characteristics can be changed, but if the additive is added in an amount exceeding 1% by weight based on the total amount of the main components, it may cause sintering. This method is excluded from the scope of the present invention because the connection becomes unstable and the no-load Q decreases.

The present invention will be explained below based on Examples*1. Starting materials include chemically high-purity BacO3, TiO2, and Sm.
2O3 and pre-prepared? I2O3・3Ti
02 was weighed to have a predetermined composition, and wet-mixed with pure water in a rubber-lined ball mill equipped with an agate ball.

After taking out this mixture from the ball mill and drying it,
It was calcined in air at a temperature of 900'C for 2 hours. The calcined product is wet-pulverized with pure water in the ball mill mentioned above.
Ta. After the crushed slurry was dehydrated and dried, 8% by weight of a 3% polyvinyl alcohol solution was added as a binder to the powder to make it homogeneous, and then the powder was sized through a 32 mesh sieve. The sized powder was molded using a mold and a hydraulic press at a pressure of 800k9/CFlf, with a diameter of 2mm and a thickness of about 1i.
It was formed into a disc. The molded body is placed in a high-purity alumina pot and heated to 1250~1250 in air depending on the composition.
The mixture was fired at a temperature within the range of 155° C. for 1 to 2 hours to obtain dielectric porcelain having the composition shown in the table. The resonant frequency, no-load Q, and dielectric constant were determined from measurements using the dielectric resonator method using the obtained ceramic element. The temperature dependence of the resonance frequency was measured in the range of -30°C to 70°C, and the temperature coefficient τf was determined. The resonant frequency was 2 to 4 GHz,
The experimental results are shown in the table. Note that the samples marked with * in the table are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention. ■ ←
! ′ 〜υ■ , −V,
As is clear from the table, the dielectric ceramic within the scope of the present invention can have a large dielectric constant and a large no-load Q value in the microwave frequency band, and also exhibits stable temperature characteristics. There is.

Therefore, the dielectric ceramic of the present invention is useful for stabilizing the temperature dependence of oscillators and resonators, and is particularly suitable for use in the UHF band due to its large dielectric constant, and is a compact and high-performance device. Can make electronic circuit parts. Furthermore, by changing the composition of the material, it is possible to select any γf within a wide range, so when a dielectric resonator is assembled using this porcelain, it is possible to maintain a temperature that eliminates the influence of surrounding metal plates on the temperature characteristics. It can have a compensatory effect. As described above, the dielectric ceramic composition of the present invention can provide useful materials not only for microwave dielectric resonators, but also for microwave substrates, dielectric adjustment rods, etc., and can be used industrially. It has great utility value.

Claims (1)

[Claims] 1 Dielectric porcelain consisting of barium oxide, titanium oxide, samarium oxide, and bismuth titanate, whose main component composition is expressed as xBaO-yTiO_2-zSm_2O_3, where x, y, and z are 5≦x≦23 (mol%) ,57≦y
≦82.5 (mol%), 2.5≦z≦37.5 (mol%
), x+y+z=100 (mol%), and bismuth titanate 2Bi_2 is in the range of the total amount with this main component.
A dielectric ceramic composition characterized in that O_3.3TiO_2 is added in an amount not exceeding 10% by weight.