JPS63138605A - Dielectric ceramic composition for microwave - 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 dielectric materials used for microwave circuit elements, microwave circuit boards, etc. is small.

The present invention relates to a dielectric ceramic composition for microwave use that has a high dielectric constant and a small temperature coefficient of dielectric constant.

(Prior Art) In recent years, with advances in microwave circuit technology, miniaturization of a single circuit has been attempted.

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 the microwave frequency band, small dielectric resonators for stabilizing the frequency of oscillators, and microwave ICs have been developed.
Dielectric porcelain is used in microwave circuits, such as dielectric porcelain used for capacitors and substrates, etc., to reduce the size of the circuit. 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.

As a porcelain material that satisfies these characteristics, T
ie, type is often used, especially Ba0-T
iO, based porcelain, and porcelain in which part of it has been replaced with other elements; and in order to adjust the temperature coefficient of dielectric constant, TiO□, which has a negative temperature coefficient, and dielectric porcelain and glass, which have a positive temperature coefficient. Many combinations have been devised and applied.

(Problems to be Solved by the Invention) Conventional Tie-based ceramic materials, 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 a 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 Problems) In view of these drawbacks, the inventors investigated various composition systems and found that the main components are calcium titanate, magnesium titanate, and neodymium titanate. The composition is x (CaTi, Ox) y (MgTiOx) z (
Nd, Tx=O,) Hx + y + z = 100
(However, X.

VeZ is the molar ratio), and the dielectric ceramic composition for microwaves which satisfies 7.5≦x≦17゜5.80≦y≦87.5.0<z≦7.5 has dielectric resonance. It has been found that this material has excellent properties as a dielectric ceramic for use in containers, microwave capacitors, substrates, etc., and is suitable for practical use.

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

The starting materials for preparing the sample are MgO, CaC0, Tie, Nd, O, with a purity of 99.5% or more.
CaTi, 0. , MgTi0. ,
Nd, Ti, 0. Each composition was weighed and put into a ball mill together with pure water for wet mixing. After drying this mixture, the calcined powder obtained by calcining for 4 hours at 800°C to 1100°C is mixed to have each predetermined composition, and then put into the ball mill again with pure water and wet-pulverized. I did it. After drying the pulverized product obtained in this way, a binder aqueous solution is added and kneaded to form a granulated powder,
Thereafter, a pressure of 2 tons/aJ was applied to create a molded body. 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 5 to 8 GHz. What is the temperature dependence of the resonant frequency?

Temperature change of resonant frequency of dielectric resonator from -20℃ to +6
It was determined by measuring between 0°C. Note that the temperature coefficient τf of the resonance frequency is approximately connected to the temperature coefficient τC of the dielectric constant by the following equation.

f=−1τC−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.

In Table 1, the samples marked with m- 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, the dielectric ceramic composition of the present invention has a relative dielectric constant of 20 or more, and the temperature coefficient of the dielectric constant is kept within a range of ±1100 pp/''C over a wide temperature range. It can be seen that the material can obtain a Q value of 4000 or more at 7 GHz, which represents the loss of a 2wI electric material.

Table 1: Nioite, CaTi, O, MgTi0. , Nd
2TizOi (7) The reason for limiting the composition range is as follows.

In other words, when CaTi, O, deviates from the predetermined amount, τf deviates from ±5opp■/°C, and MgTi0. When deviates from the predetermined amount, εr and Q decrease, and Nd, Ti, 0
When □ exceeds a predetermined amount, τf becomes less than 150 ppm/'C, and when it is zero, τf becomes +5 opp■/'
This is because it is larger than C.

(Effects of the Invention) As described above, the dielectric ceramic composition according to the present invention has a large dielectric constant of 20 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. 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] The main component is calcium titanate [CaTi_2O_5]
and magnesium titanate [MgTiO_3] and neodymium titanate [Nd_2Ti_2O_7],
Its main component composition is x[CaTi_2O_5)y(MgT
iO_3〕z(Nd_2Ti_2O_7〕, x+y+z
= 100 (where x, y, z are molar ratios), 7.5≦x≦17.5, 80≦y≦87.5, 0<z
A dielectric ceramic composition for microwave use, characterized in that ≦7.5.