JPH069125B2 - High frequency dielectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is applied in the micro frequency range, exhibits a high Q value in this range, and has a dielectric constant that can be put to practical use and stable. The present invention relates to a dielectric ceramic composition having temperature characteristics.

<Prior Art> With the development of communication networks in recent years, the frequency range used has expanded to reach microwaves. In connection with this, the dielectric ceramics are applied to impedance matching of dielectric resonators, microwave integrated circuit boards, and various microwave circuits in the microwave frequency range. Especially recently, filters and guns or F
A large number of ET microwave oscillators are required for frequency stabilization, and the demand for them is increasing.

However, the dielectric loss tends to increase as the frequency used increases. So in the micro frequency range,
A dielectric porcelain having a large Q value is desired.

<Problems to be Solved by the Invention> Zr is a conventional general high-frequency dielectric ceramic material.
There are O ₂ —SnO ₂ —TiO ₂ system porcelain, BaO—TiO ₂ system porcelain, and porcelain in which a part thereof is replaced with other elements.

However, these materials have various problems such as a small Q value, a small relative dielectric constant, and a failure to obtain a desired temperature coefficient.

It is an object of the present invention to provide a high frequency dielectric ceramic composition having a high Q value applicable to the microwave region, a dielectric constant that can be put to practical use, and stable temperature characteristics. .

<Means for Solving Problems> In the present invention, a composition comprising BaO in an amount of 15 to 25 mol% and TiO _{2 in an amount} of 75 to 85 mol% is added to La ₂ O ₃ , Fe ₂ O ₃ , and Ta _2. A dielectric ceramic composition for high frequencies, comprising one or more metal oxides of the group consisting of O ₅ in a total amount of 0.1 to 1.2% by weight and further containing less than 0.5% by weight of MnO ₂ .

<Example> The present invention was carried out as follows.

・ Sample: BaCO ₃ , TiO ₂ , and MnO ₂ having a purity of 99.9% are used as a starting material, and predetermined amounts are weighed and mixed according to each composition, and the mixture is subjected to dry primary pulverization and mixing with a mixer, and then 1000 ° C. in air. Calcination at the temperature of 6 hours. Further, one or more kinds of metal oxides of the group consisting of La ₂ O ₃ , Fe ₂ O ₃ , and Ta ₂ O ₅ were added to this calcined product, and secondary pulverization and mixing by dry method were again performed with a mixer. Then, it is calcined in the atmosphere at a temperature of 1000 ° C. for 6 hours. Next, an appropriate amount of an organic binder and water are added to this calcined product, which is crushed with an alumina ball of 30 mmφ and then granulated by spray drying. This granulated raw material is pressed at a pressure of 1500 Kg / cm ² for 15 mm.
It is shaped into a disk with a size of φ x 10 mmt. Next, this shaped body is fired in the atmosphere at a temperature of 1300 ° C to 1420 ° C for 10 hours. Finally, it is polished into a disk shape of 9 mmφ x 5 mmt, and silver electrodes are baked on the front and back surfaces to make dielectric samples, and the Q value (= 1 / ttanδ), dielectric constant ε, and resonance frequency temperature coefficient τf are measured for each. To do.

- For samples added test value La ₂ O _3, results obtained by examining the properties were as shown in the first table corresponding to the blending composition.

The values of the dielectric constants ε and Q in the table are measured by the dielectric resonator method. The resonance frequency temperature coefficient τf is −
It was determined from the value in the temperature range of 30 ° C to + 80 ° C based on the following formula.

[tau] f = -1 / 2 [tau]-[alpha] where [tau]; temperature change rate of permittivity [alpha]; linear expansion coefficient of porcelain sample Also, the resonance frequency was 6.9 GHz.

In each of the following tables, sample numbers surrounded by circles are outside the scope of the present invention.

The results of adding Fe ₂ O ₃ and Ta ₂ O ₅ instead of La ₂ O ₃ are shown in Tables 2 and 3, respectively.

-Results As is clear from the above table, the dielectric ceramic material of the present invention has a high Q value of 4000 or more in the microwave region, and the dielectric constant ε and the resonance frequency temperature coefficient τf can be put to practical use. It was shown to be.

In addition, in the above-mentioned examples, MnO ₂ is added in a small amount for improving the sinterability, and does not directly improve the Q value. However, the addition amount becomes excessive at 0.5% by weight or more, and the Q value becomes 3000 or less as in the case of Sample 8, so that the addition amount is limited.

<Reason for limiting the present invention> Next, the reason for limiting the composition range of the present invention will be described. B) La ₂ O ₃ , Fe ₂ O ₃ , and Ta ₂ O ₅ cannot be expected to have an improved Q value as in Samples 5, 6, 23, and 44 when the addition amount exceeds 1.2% by weight. .

Further, since the action of each metal oxide is equal, even when two or more kinds thereof are added, the improvement of the Q value cannot be expected when the total amount exceeds 1.2% by weight. (B) When BaO is less than 15 mol%, the Q value is low and τf takes a large positive value like Sample 12. C) When the BaO content exceeds 25 mol%, the Q value remarkably decreases as in Sample 10. D) MnO ₂ is added in a small amount to improve the sinterability, and does not directly improve the Q value.
However, the addition amount becomes excessive at 0.5% by weight or more, and the Q value becomes 3000 or less as in the case of Sample 8, so that the addition amount is limited.

Therefore, the above range is excluded from the scope of the present invention.

<Effects of the Invention> The dielectric porcelain composition according to the present invention has a high Q value, and the values of the dielectric constant and the resonance frequency temperature coefficient can be suitable for practical use, as has been clarified in the experimental examples.

Therefore, the present invention is most suitable as a dielectric ceramic material applied to the micro frequency range.

Claims (1)

[Claims] 1. BaO 15 to 25 mol% and TiO ₂ 75 to 85
A total of 0.1 to 1.2% by weight of one or two or more metal oxides of the group consisting of La ₂ O ₃ , Fe ₂ O ₃ , and Ta ₂ O _{5 is} added to the composition having a mol% distribution. A high-frequency dielectric porcelain composition comprising 0.5% by weight of MnO ₂ .