JPH0829981B2 - High frequency dielectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high frequency dielectric ceramic composition.

(Prior Art) In recent years, dielectric ceramics have been widely used in the microwave region, such as the practical use of car telephones and personal radios, the development of ICs for microwave circuits, and the application to gun oscillators. Such high-frequency dielectric porcelain is mainly used for resonators, and the characteristics required therefor are (1) The dielectric constant is large to meet the demand for miniaturization (2) The dielectric loss at high frequencies is small, and (3) The change in resonance frequency with temperature is small, that is, the dielectric constant has temperature dependence. It must be small and stable, and the above three characteristics can be mentioned.

Conventionally, as a dielectric ceramic of this type, for example, BaO-TiO
₂ material, ReO-BaO-TiO ₂ based materials and (BaSr) (ZrTi) O ₃
System materials are known.

(Problems to be Solved by the Invention) However, in the BaO-TiO ₂ system material, the dielectric constant is εr = 3.
It is as high as 8 to 40, and the dielectric loss is small as tan δ <2.00 × 10 ^-4 , but it is difficult to obtain a resonance frequency temperature coefficient τf = 0 in a single phase. Since the change in dependency is large, it is difficult to stably control the temperature coefficient (τf) of the resonance frequency to be small while maintaining a high dielectric constant and a low dielectric loss. In addition, ReO ~ BaO-Ti
The O ₂ system has a very high dielectric constant of εr = 40 to 60 and a temperature coefficient τf = 0 of the resonance frequency can be obtained, but the dielectric loss is large as tan δ> 5.0 × 10 ⁻⁴ . Furthermore (BaSr) (ZrTi)
In the O ₃ system, the dielectric loss is small as tan δ <2.00 × 10 ^−4, and the one having the temperature coefficient τf = 0 of the resonance frequency can be obtained, but the dielectric constant is very small as εr = 29 to 35. The dielectric constant (ε
r) and dielectric loss (tan δ) are 500 by the semi-coaxial resonator method.
Measured at ~ 600 MHz. As described above, none of the above-mentioned materials sufficiently satisfy the three characteristics required for the high-frequency dielectric material.

(Means for Solving Problems) As a result of intensive research in view of the above-mentioned present situation, the present invention mainly includes a mixed composition of strontium oxide (SrO), nickel oxide (NiO), and niobium oxide (Nb ₂ O ₅ ). , A composition formula (1) obtained by adding a mixed composition of calcium oxide (CaO) and titanium oxide to this main component (1) (1-X) Sr (Ni1 / 3Nb2 / 3) O ₃ · XCaTiO ₃ …… (1) However, the ceramic composition represented by 0 <X ≦ 0.6 has a high dielectric constant and maintains a low dielectric loss for high frequencies, and exhibits a stable temperature dependence and a small temperature dependence of the resonance frequency. This has led to the present invention.

The porcelain composition represented by the composition formula (1) in the present invention is itself a single phase of a perovskite type crystal structure in which CaTiO ₃ is formed as a solid solution with Sr (Ni1 / 3Nb2 / 3) O _3. , Sr
The composition ratio of O, NiO, Nb ₂ O _{5 and} the composition of CaO and TiO ₂ are composed of the respective ratios shown in the composition formula (1). If these ratios are deviated, the perovskite type crystal structure is broken. At the same time, it loses the excellent dielectric properties at the same time.

In the composition formula (1), the X value is in the range of 0 <X ≦ 0.6. When X> 0.6, the dielectric loss is large and the Q value is low, and the temperature coefficient of the dielectric constant is large. Particularly preferable X value is 0.1 ≦ X ≦ 0.5.

Example Preparation of sample Using high-purity strontium carbonate (SrCO ₃ ), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ), calcium carbonate (CaCO ₃ ), and titanium oxide (TiO ₂ ) First
It was weighed so as to have the ratio shown in the composition column of the table, and wet-mixed all day and night using agate boulders. After drying this mixture, it is calcined at 1,300 ° C for 2 hours, further added about 1% by weight of binder, and then sized. The powder obtained is about 800K.
It was molded at a pressure of g / cm ² and calcined in air at a temperature in the range of 1,400 ° C to 1,700 ° C for 2 hours.

Measurement of characteristics The dielectric constant, the dielectric loss, and the temperature coefficient of the resonance frequency of the obtained sample were measured by the dielectric cylinder resonator method (post-resonator method) at the resonance frequency of 4.5 to 9 GHz. The results are shown in Table 1.

As is clear from Table 1, the sample No. 1 containing no CaTiO ₃ has a small dielectric constant, and the sample No. 8 with X> 0.6 has a large dielectric constant but a large dielectric loss, resulting in a small Q value. The temperature coefficient of the resonance frequency was also large. On the other hand, Sample Nos. 2 to 7 of the present invention all show excellent dielectric properties, having a dielectric constant of 30 or more, a Q value of 2200 or more,
A characteristic of | τf | of 80 or less was obtained, and particularly in the range of 0.1 ≦ X ≦ 0.5, excellent characteristics of dielectric constant of 30 or more, Q value of 2300 or more, and | τf | 33 or less were exhibited.

(Effects of the Invention) As described in detail above, the high-frequency dielectric ceramic composition of the present invention has the same composition of CaO and TiO ₂ as the ceramic composition of perovskite type crystal structure of SrO, NiO and Nb ₂ O ₅ . By forming a single-phase perovskite-type crystal by forming a solid solution of a porcelain composition having a crystal structure, it is possible to obtain high dielectric constant, low dielectric loss, and low temperature coefficient of resonance frequency for high frequencies. . As a result, it is possible to obtain a material that is satisfactory for use as a resonator or a circuit board material, and at the same time, it is possible to reduce the size.

Claims (1)

[Claims] 1. A high frequency dielectric ceramic composition having a composition formula of (1-X) Sr (Ni1 / 3Nb2 / 3) O ₃ .XCaTiO ₃ where 0 <X ≦ 0.6.