JPS62283862A - 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] Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a dielectric material used for microwave circuit elements, microwave circuit boards, etc., which is obtained by firing a metal oxide. The present invention relates to a dielectric ceramic composition having a high dielectric constant, low dielectric loss, and a small 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 11' (300MH
Cavity resonators, antennas, and the like have been used in circuits for 30 GII (z~30GIIz), but these are not suitable for miniaturizing circuits because their size is about the same as the wavelength of a microwave. 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, capacitors and boards for microwave ICs, etc. Applications have been made to miniaturize circuits by using dielectric ceramics in microwave circuits. The characteristics required of these porcelains are low dielectric loss in the microwave frequency band,
It has a high dielectric constant suitable for the frequency band used, and the temperature coefficient of the dielectric constant is small.

Ti has traditionally been used as a porcelain material that satisfies these characteristics.
O□ type materials are often used, especially BaO-Ti
O2-based porcelain, porcelain in which part of it has been replaced with other elements, and TiO□, which has a negative temperature coefficient, and dielectric porcelain and glass, which have a positive temperature coefficient, to adjust the temperature coefficient of dielectric constant. Many combinations have been devised and applied.

(Problems to be solved by the invention) Conventional TiO2-based, especially Bad-Tie2-based ceramic materials have problems such as not having a sufficiently high dielectric constant, not having a sufficiently small dielectric loss, not being able to obtain a desired temperature coefficient, etc. However, it is difficult to stably obtain a material that satisfies all the properties, 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 component composition was calcium titanate (C
aTiO,) and lanthanum titanate [La, Ti, 0. )
and magnesium neodymium titanate [Nd (Mg'
/z Tl '/2) Oi: A mixture of I, magnesium titanate, and zinc oxide [MgTiO3.±ZnO)
The main component composition is x(CaTiO,) ・y
[LazTizOt) ・Z[Nd(Mg7zTi7z
)0, :l+w[MgTiO3・-1Zno), x+
When expressed as y+z=100 (X!YTZI cod molar ratio), x+Y+Zrw is 10≦x≦75.0≦
A dielectric ceramic composition in which y≦25.15≦2≦75, 5≦≦≦40 has excellent properties as a dielectric ceramic used for vI dielectric resonator microwave capacitors, substrates, etc., and has been put into practical use. It was found that this material is suitable for use in

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

The starting materials for preparing the samples are MgO, CaC0, Tie, Nd2O, with a purity of 99.9% or more.
, La, 03 and ZnO powder, Ca, T
iOs and La, Ti20. and Nd (Mg!'z Ti
'/l)03 and MgTi0z.xZno, and put them into a ball mill together with pure water for wet mixing. After drying this mixture, 800
The calcined powder obtained by calcining at ~1100° C. for 4 hours 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 obtained in this way, the granulated powder obtained by adding and kneading an aqueous binder solution was subjected to a pressure of 1.5 ton/cm", and the resulting molded body was heated at 1200°C to 1500°C. A fired body was obtained by firing in air at ℃ for 2 hours.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 of the obtained dielectric resonator is 4 to 8 GHz
Met. The temperature dependence of the resonant frequency was determined by measuring temperature changes in the resonant frequency of the dielectric resonator between +25°C and +85°C. Note that the temperature coefficient τf of the resonance frequency is approximately connected to the temperature coefficient τε of the dielectric constant by the following equation.

τf=−1 τ E −α Also, 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 this table, the samples marked with a book 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, the dielectric ceramic composition of the present invention has a relative permittivity of 30 or more, and the temperature coefficient of the permittivity is within a wide temperature range of ±1100 pp/''C. It can be seen that the material is capable of suppressing the loss of the dielectric material, and can obtain a Q value of 2000 or more at frequencies in the microwave band.

Further, in the present invention, the reason for limiting the component range is as follows. For (CaTi0.), if it is less than 10 moles, the Q will be low, and if it is more than 75 moles, the temperature coefficient will be large;
When the amount is more than 5 mol, Q becomes low and [Nd (Mg, T
i7□)03], if it is less than 15 mol, the temperature coefficient becomes large, and if it is more than 75 mol, Q becomes small, and for (MgTie, ・7 Z n O), 5
This is because if it is less than 40 moles, a high sintering temperature is required, and if it is more than 40 moles, ε will be low and the temperature coefficient will be large.

(Effects of the Invention) As described above, the dielectric ceramic composition according to the present invention is a material having a large dielectric constant of about 50 at microwave frequencies, low dielectric loss, and a small temperature coefficient of dielectric constant. It can be seen that it is.

Claims (1)

[Claims] The main components are calcium titanate [CaTiO_3], lanthanum titanate [La_2Ti_2O_7], and magnesium neodymium titanate [Nd(Mg_1_/_2T)]
i_1_/_2)O_3] and a mixture of magnesium titanate and zinc oxide [MgTiO_3・1/2ZnO], whose main component composition is x[CaTiO_3]・y[L
a_2Ti_2O_7]・z[Nd(Mg_1_/_2
Ti_1_/_2)O_3]+w[MgTiO_3・1
/2ZnO], x+y+z=100 (x, y, z
, w is the molar ratio), when x, y, z, w are 10
≦x≦75, 0≦y≦25, 15≦z≦75, 5≦w≦
Microwave dielectric ceramic composition characterized by having a