JPH07112951B2 - 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 in response to the demand for downsizing, (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's temperature dependence. Is small and stable, and the above three characteristics are mentioned.

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

(Problems to be Solved by the Invention) However, although the BaO—TiO ₃ system material has a high dielectric constant and a small dielectric loss, it is difficult to obtain a single phase having a resonance frequency temperature coefficient τf = 0. Since the change in the dielectric constant and the temperature dependency of the dielectric constant with respect to the composition change are large, it is difficult to stably control the temperature coefficient (τf) of the resonance frequency to be small while maintaining the high dielectric constant and the low dielectric loss. Further, the dielectric constant in the ReO-BaO-TiO ₂ system is very high, also it can be obtained that temperature coefficient .tau.f = 0 of the resonance frequency, the dielectric loss is large. Further, in the (BaSr) (ZrTi) O ₃ system, the dielectric loss is small, and the one having the temperature coefficient τf = 0 of the resonance frequency can be obtained, but the dielectric constant is small. As described above, in any of the above materials, the above-mentioned 3 required for the high frequency dielectric material is used.
Not fully satisfied based on the characteristics.

(Means for Solving Problems) The present invention has been made as a result of intensive research in view of the above-mentioned present situation, and strontium oxide (SrO), nickel oxide (NiO), niobium oxide (Nb)
₂ O ₅ ) as a main component, and a composition formula (1) (1-X) Sr obtained by adding a mixed composition of strontium oxide (SrO) and titanium oxide (TiO ₂ ) to this main component (Ni1 / 3Nb2 / 3) O ₃ XSrTiO ₃ (1) However, the ceramic composition represented by 0 <X ≦ 0.4 has a high dielectric constant and maintains a low dielectric loss for high frequencies, and The inventors have found that the temperature dependence of the resonance frequency is small and exhibit stable characteristics, and have reached 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 SrTiO ₃ forms a solid solution with Sr (Ni1 / 3Nb2 / 3) O _3. , SrO,
The composition ratio of NiO, Nb ₂ O _{5 and} the composition of SrO 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 and a single phase is formed. At the same time, the excellent dielectric properties deteriorate.

In the composition formula (1), the X value is in the range of 0 <X ≦ 0.4. When X> 0.4, the dielectric loss is large, the Q value is low, and the temperature coefficient of the dielectric constant is large. Particularly preferred X
The value is 0.1 ≦ X ≦ 0.3.

Example Preparation of sample High-purity strontium oxide (SrCO ₃ ), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ) and titanium oxide (Ti
O ₂ ) was weighed so that the X value was in the proportion shown in the composition column of Table 1, 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 a binder, and then sized, and the obtained powder is molded at a pressure of about 800 kg / cm ² , Firing was performed in air at a temperature in the range of ℃ to 1,700 ℃ for 2 hours.

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

As is clear from Table 1, No. 1 sample containing no SrTiO ₃ has a small dielectric constant, and X> 0.4 has No. 7 and No.
Sample No. 8 had a large dielectric constant but a large temperature coefficient of resonance frequency. On the other hand, Sample Nos. 2 to 6 of the present invention all show excellent dielectric properties and
Characteristic of 30 or more, Q value of 1700 or more and | τf | of 62 or less are obtained. Especially in the range of 0.1 ≦ X ≦ 0.3, the dielectric constant is 30 or more and the Q value is 17
Excellent characteristics of 00 or more and | τf | 38 or less were shown.

(Effects of the Invention) As described in detail above, the high frequency dielectric ceramic composition of the present invention is
SrO, NiO, Nb ₂ O ₅ perovskite type crystal structure porcelain composition, SrO, TiO ₂ of a similar crystal structure porcelain composition in a specific proportion to form a solid solution, single-phase perovskite type By forming a crystal, high dielectric constant, low dielectric loss, and small temperature coefficient of resonance frequency can be obtained with respect to high frequency. 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 .XSrTiO ₃ provided that 0 <X ≦ 0.4.