JPS63112459A - Dielectric ceramic composition for microwave - Google Patents

Abstract

(57) [Abstract] 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 dielectric materials used for microwave circuit elements, microwave circuit boards, etc. The present invention relates to a dielectric ceramic composition for microwave use that has a small dielectric constant, a high dielectric constant, and a small temperature coefficient of the dielectric constant.

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

Conventionally, this microwave frequency band (300MHz ~
Cavity resonators, antennas, etc. have been used in circuits for 30GH2), 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 the microwave frequency band, small dielectric resonators for stabilizing the frequency of oscillators, microwave I
Dielectric ceramics used for C capacitors and substrates, etc.
Dielectric ceramics 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.

Ti has traditionally been used as a porcelain material that satisfies these characteristics.
O2-based materials are often used, especially Ba0-Ti
In order to adjust the temperature coefficient of dielectric constant, Tie, which has a negative temperature coefficient, and dielectric porcelain and glass, which have a positive temperature coefficient, are available. Many combinations have been devised and applied.

(Problems to be solved by the invention) Conventional TiO□-based, especially Bad-Tie, based porcelain materials do not have a sufficiently high dielectric constant, do not have a sufficiently small dielectric loss, or cannot obtain the desired temperature coefficient. It is difficult to stably obtain a material that satisfies all of the properties, such as the absence of carbon dioxide, and there are many problems in practical use.

(Means for solving the problem) As a result of studying various composition systems in view of these drawbacks, the inventors found that the main component composition consists of titanium oxide, calcium oxide, and neodymium oxide. xc
ao-yTio,-zNdO,7,, x + y +z
= 1 (where X, y, z are molar ratios), 0
．． 025≦x≦0.30.0.40≦y≦0.70.0
．． A microwave dielectric ceramic composition in which 2≦z≦0.40, and a main component composition consisting of titanium oxide, calcium oxide, and neodymium oxide, the main component composition being xcao
-yTioz-zNdozz t X + y+ Z
= 1 (However, X.

'J+Z is molar ratio), 0.025≦x≦
0゜30, 0.40≦y≦0.70.0.2≦z≦0.
40, and lead oxide is 15% + 1% or less (not including O)
The dielectric ceramic composition for microwaves containing additives in the range of 100% has excellent properties as a dielectric ceramic composition used for dielectric resonators, microwave capacitors, substrates, etc., and is a material suitable for practical use. I discovered something.

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

The starting materials for preparing the samples are Tie□, CaC0,, Nd, O, r PbO with a high purity of 99.5% or more.
Each of the powders was weighed so as to have a predetermined composition, and then put into a ball mill together with pure water for wet mixing.

After drying this mixture, it was heated at 800℃ to 1100℃ for 4 hours.
The calcined powder obtained by calcining for a period of time was mixed to have each predetermined composition, and then put into the ball mill together with pure water again for wet pulverization. After drying the pulverized product thus obtained, an aqueous binder solution was added and kneaded to obtain a granulated powder, and then a pressure of 2 ton/ci was applied to form a molded product. This molded body was fired in air at 1200°C to 1400°C for 2 hours to obtain a fired body. A dielectric resonator was constructed using the obtained fired ceramic, and the resonant frequency and no-load Q of the dielectric resonator were measured to determine the dielectric constant. The resonant frequency of the obtained dielectric resonator was 3 to 5 GHz. The temperature dependence of the resonant frequency was determined by measuring the temperature change of the resonant frequency of the dielectric resonator between -20°C and +60°C. Note that the temperature coefficient τf of the resonance frequency is the temperature coefficient τE of the dielectric constant.
It is approximately connected by the following equation.

f=--τε-α where τf: Temperature coefficient of resonance frequency τε: Temperature coefficient of dielectric constant α: Coefficient of thermal expansion of porcelain The measurement results for the obtained samples are shown in Table 1. The samples marked with disclosure in this table are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention. Among these examples, those in which the amount of PbO added is 0 are examples of the first invention of the present application, and the others are examples of the second invention of the present application.

As shown in Table 1, the dielectric ceramic composition of the present invention has a relative dielectric constant of 50 or more, and the temperature coefficient of dielectric constant is ±1100 pp/'C over a wide temperature range.
It can be seen that this material can be kept within the range of 1,000 or more at frequencies in the microwave band, and the Q value representing the loss of the dielectric material can be kept within the range of 1,000 or more.

Table 1 In the first invention of the present application, Cab, Tie, Nd
The reason for limiting the composition range of O, 7° is as follows.

In other words, when CaO deviates from the predetermined amount, εr and Q decrease, and when TiO□ deviates from the predetermined amount, εr decreases, and Nd
If 03/2 is less than 0.2, τf is +1100pp
/''C, and if Nd01/□ is more than 0.4, τf becomes less than 1100 ppm/'C.

Further, in the second invention of the present application, Cab, Tie,...
The reason why the composition range of Nd01/2 was limited is the same as the above reason, and the reason why the amount of PbO added was set to 15 wt% or less is that if more than this amount is added, the Q will decrease.

(Effects of the Invention) As described above, the dielectric ceramic composition according to the present invention has a large dielectric constant of 50 or more at microwave frequencies, a small dielectric loss, and a small temperature coefficient of the dielectric constant. You can see that it is the material.

It is clear that these dielectric ceramic materials are extremely useful as circuit elements and substrates used in the microwave frequency band. Note that this material has a vI electric loss of tJ even in the low frequency range.
It was confirmed that it is an excellent material as a capacitor material with high % thickness and Q value.

Claims (1)

[Claims] 1. The main component composition consists of titanium oxide, calcium oxide, and neodymium oxide, and the main component composition is xCaO-yT.
When expressed as iO_2-zNdO_3_/_2, x+y+z=1 (however, x, y, z are molar ratios), 0.025
≦x≦0.30, 0.40≦y≦0.70, 0.20≦
A dielectric ceramic composition for microwave use, characterized in that z≦0.40. 2. The main component composition consists of titanium oxide, calcium oxide, and neodymium oxide, and the main component composition is xCaO-yT.
When expressed as iO_2-zNdO_3_/_2, x+y+z=1 (however, x, y, z are molar ratios), 0.025
≦x≦0.30, 0.40≦y≦0.70, 0.20≦
A dielectric ceramic composition for microwave use, characterized in that z≦0.40 and lead oxide is added in an amount of 15 wt% or less (excluding 0).