JPS61291454A - Dielectric ceramic ceramic composition - 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 (Field of Industrial Application) The present invention relates to dielectric materials used in microwave circuit elements, microwave circuit boards, etc. The present invention relates to a dielectric ceramic composition with low dielectric loss and low temperature coefficient of dielectric constant.

(Prior Art) In recent years, with advances in microwave circuit technology, circuits have been made smaller.

Conventionally, this microwave frequency band (300MHz to 3
Cavity resonators, antennas, and the like have been used in circuits of 0 GHz), but these are not suitable for miniaturizing circuits because their size is about the same as the wavelength of microwaves. In contrast, in recent years, microwave filters using dielectric resonators used in several microwave frequency bands, small dielectric resonators for stabilizing the frequency of oscillators, capacitors and substrates for microwave ICs, etc. Dielectric ceramics, such as dielectric ceramics used in microwave circuits, etc., have been used in microwave circuits to reduce the size of the circuits. The characteristics required of these ceramics are that they have low dielectric loss in the microwave frequency band, a high dielectric constant suitable for the frequency band used, and a small temperature coefficient of dielectric constant.

Tl has traditionally been used as a porcelain material that satisfies these characteristics.
O2-based materials are often used, especially Ba0-Ti
Oz-based porcelain and porcelain in which part of it is replaced with other elements,
In order to further adjust the temperature coefficient of dielectric constant.

Many devices have been devised and applied that combine Tie, which has a negative temperature coefficient, with dielectric porcelain or glass, which has a positive temperature coefficient.

(Problems to be Solved by the Invention) Conventional TiO□-based, especially Ba0-TiO□-based porcelain materials have a dielectric constant that is not high enough, a dielectric constant that is not small enough, or a desired temperature coefficient cannot be obtained. It is difficult to stably obtain a material that satisfies all properties, such as
There were many practical problems.

(Means for Solving the Problems) In view of these drawbacks, the inventors investigated various composition systems, and found that xBaO-yTio, -zs+m, 03
In the composition represented by 10≦x≦30 (mol%),
50≦y≦80 (mol%), 5≦z≦40 (mol%),
With respect to the main component in the range of x + y + z = 100 (mol%), Teo is 3% by weight or less (but 0
The dielectric ceramic composition containing additives (excluding weight percent) has excellent properties as a dielectric ceramic used for dielectric resonators, microwave capacitors, substrates, etc., and is a material suitable for practical use. I found it.

(Example) The present invention will be explained below according to examples.

The starting material for preparing the sample is BaCO3, Tie□, 5ff120. of high purity of 99.9% or more. and TeO2 powders were weighed to give each predetermined composition, and put into a ball mill together with pure water for wet mixing.

After drying this mixture, it was calcined at 1000°C for 4 hours.

Thereafter, the granulated powder obtained by adding and kneading an aqueous binder solution was heated to a pressure of 1.5 ton/cm", and the resulting molded body was fired in air at 1300°C to 1500°C for 2 hours to form a fired body. After that, a dielectric resonator was constructed using the obtained ceramic, and the resonant frequency and no-load Q of the dielectric resonator were measured to determine the dielectric constant. The resonant frequency was 2 to 4 GHz.The temperature dependence of the resonant frequency was determined by measuring the temperature change of the resonant frequency of the dielectric resonator between +25°C and +85°C.The temperature coefficient of the resonant frequency τf is approximately connected to the temperature coefficient τε of the dielectric constant by the following equation.

τf=−−τε−α In addition, τf; Temperature coefficient of resonance frequency τε: Temperature coefficient of dielectric constant α: Coefficient of thermal expansion of porcelain. Table 1 shows the measurement results for the obtained samples. In this table, the samples marked with an umbrella mark are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention.

As shown in Table 1, when the amount of BaO (x) exceeds 30 mol% or the amount of TiO□ (y) is less than 50 mol%, it becomes difficult to sinter the porcelain, and the no-load Q decreases. , is excluded from the scope of the present invention because it cannot be measured.

Also, if X is less than 10 mol%, or if 2 is 4
If it exceeds 0 mol%, sintering of the porcelain becomes unstable and the no-load Q decreases. Furthermore, if y exceeds 80 mol%, the sintering of the porcelain becomes unstable and the temperature characteristics change significantly, so it is excluded from the scope of the present invention.

Further, with regard to the addition of Too, which is a subcomponent, as the amount added increases, the sintering temperature of the porcelain can be lowered and the no-load Q can be increased. However, if it is added in an amount exceeding 3% by weight, the dielectric constant and the no-load Q will be significantly lowered, so it is excluded from the scope of the present invention.

Table 1 (Effects of the Invention) As described above, the dielectric ceramic composition according to the present invention has a large dielectric constant of about 80 at microwave frequencies, a small dielectric loss, and a temperature coefficient of the dielectric constant. It can be seen that this is a small material.

It is clear that these dielectric ceramic materials are extremely useful as circuit elements and substrates used in the microwave frequency band. It was confirmed that this material has low dielectric loss even in the low frequency range and is an excellent material for capacitors with a high Q value.

Claims (1)

[Claims] When expressed as the compositional formula xBaO-yTiO_2-zSm_2O_3, x, y, z are 10≦x≦30 (mol%),
50≦y≦80 (mol%), 5≦z≦40 (mol%),
x+y+z=100 (mol%), and TeO_2 is 3% by weight or less (however, 0% by weight) based on this main component.
A dielectric ceramic composition characterized by containing a composite additive of (excluding).