JP2691302B2 - Dielectric porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel dielectric ceramic composition suitable as a resonator or circuit board material in a microwave region.

(Prior art) In recent years, microwave circuits have been developed with the practical use of car phones, cordless telephones, personal radios, and satellite broadcast receivers.
Dielectric ceramics in the microwave region are widely used, such as development to IC, expansion of the use range of gun oscillators, and application to oscillators using gallium arsenide field effect transistors.

Such microwave dielectric porcelains are mainly used for resonators, and the characteristics required therefor are: (1) In the dielectric, the wavelength is shortened to 1 / εr ^1/2 , Large relative permittivity against requirements, (2) Small dielectric loss at high frequencies, (3) Small change in resonance frequency with temperature, that is, small relative temperature dependency of relative permittivity and stable. There are three main characteristics mentioned above.

Conventionally, as this type of dielectric ceramic, for example, BaO-T
An iO ₂ -based material, a BaO-REO-TiO ₂ (where REO is a rare earth oxide, the same applies hereinafter) -based material, a MgTiO ₃ -CaTiO ₃ -based material, and the like are known.

(Problems to be Solved by the Invention) However, the relative dielectric constant εr of the BaO—TiO ₂ based material is 38.
40 and high and although the dielectric loss tanδ is as small as 2.0 × 10 ^-4, a single-phase hard to obtain those temperature dependence τf of the resonance frequency is zero, the temperature of the dielectric constant and the dielectric constant for the composition change Since the dependence greatly changes, it is difficult to stably control the temperature coefficient τf of the resonance frequency to be small while maintaining a high relative dielectric constant and a low dielectric loss.

Also, the BaO-REO-TiO ₂ based materials BaO-Nd ₂ O ₃ -
TiO ₂ system or BaO-Sm ₂ O ₃ -TiO ₂ system and the like are known, but in these systems, the dielectric constant εr is as high as 40 to 60,
Although the one having a zero temperature coefficient τf of the resonance frequency has been obtained, the dielectric loss tan δ is as large as 5.0 × 10 ^-4 or more.

Furthermore, in the MgTiO ₃ -CaTiO ₃ system, the dielectric loss tanδ is 2.0 × 10
^-4f or less, and a temperature coefficient τf of the resonance frequency of zero is obtained, but the dielectric constant is as small as 16 to 25.

As described above, none of the above-mentioned materials sufficiently satisfies the three characteristics required for the high-frequency dielectric material.

(Object of the Invention) The present invention has been devised in view of the above-mentioned drawbacks, and has a high dielectric constant (30 or more) in order to enable the miniaturization of a resonator.
It is an object of the present invention to provide a high-frequency dielectric ceramic composition having a low dielectric loss and a small and stable temperature dependence of a dielectric constant, and a small and stable temperature dependence of a resonance frequency of a dielectric resonator. .

(Means for Solving Problems) As a result of repeated studies on the above problems, the present inventors have found that barium oxide (BaO) and samarium oxide (Sm ₂ O ₃ )
Composition formula (1) Ba Sm _1/2 (Nb _x Ta _1-x ) _1/2 O ₃ · obtained by individually or in combination with niobium oxide (Nb ₂ O ₅ ) or tantalum oxide (Ta ₂ O ₅ ). .. (1) However, the ceramic composition represented by 0 ≦ x ≦ 1 has a high dielectric constant for high frequencies and maintains a low dielectric loss, and the temperature dependence of the resonance frequency is small and stable characteristics. Therefore, the present invention has been completed.

The dielectric ceramic composition of the above formula (1) in the present invention is
A complex perovskite crystal structure composed of two or three ions of Sm, Nb, and Ta, as represented by the site Ba and the site B Sm _1/2 (Nb _x Ta _1-x ) _1/2 If the composition ratio is out of the respective ratios shown in the above formula (1), the perovskite type crystal structure collapses, the composition is not a single phase, and at the same time excellent dielectric properties are deteriorated.

In the case of producing a porcelain in the present invention, an oxide of a metal constituting the porcelain, that is, BaO, Sm ₂ O ₃ , Nb ₂ O _{5 and} Ta ₂ O ₅ or can be converted to the oxide by firing, for example, Compounds such as carbonates, nitrates and sulfates are weighed and mixed, and then calcined at 1200 to 1500 ° C. if desired. After molding this mixture or calcined powder, it is fired in the air at 1500 to 1700 ° C. to obtain a porcelain.

 Hereinafter, the present invention will be described with reference to the following examples.

(Example) Using high-purity barium carbonate (BaCO ₃ ), samarium oxide (Sm ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), and tantalum oxide (Ta ₂ O ₅ ) powders as starting materials Was weighed so that the x value in the above formula (1) was in the ratio shown in Table 1, and then pure water was added and wet mixing was performed overnight using agate stones. After this mixture was dried, it was calcined at 1400 ° C for 2 hours, further added with about 1% by weight of a binder, and then sized, and the obtained powder was molded under a pressure of about 1000 kg / cm ² , 17
Calcination was performed in air at a temperature of 00 ° C. for 2 hours.

The obtained porcelain was subjected to surface polishing and cylindrical grinding to obtain a distortion-free cylindrical sample having a diameter of about 8 mm and a height of about 4 mm. Using this sample, a resonance frequency of 8 was obtained by the dielectric cylinder resonator method.
Measure dielectric constant (εr), dielectric loss tanδ, temperature coefficient of resonance frequency (τf) at 1010 GHz, τf is −40 to + 85 ° C.
Was measured. The results are shown in Table 1.

As is clear from Table 1, the dielectric material of the present invention has characteristics of relative permittivity of 33 or more, Q value of 4000 or more, and τf of 25 (ppm / ° C) or less, and the composition ratio of Nb and Ta. By changing the value, excellent characteristics capable of controlling τf within the range of +1 to 23 (ppm / ° C) were obtained.

(Effect of the Invention) As described in detail above, the dielectric ceramic composition of the present invention is
By forming a composite perovskite type crystal structure consisting of O, Sm ₂ O ₃ , Nb ₂ O ₅ and Ta ₂ O ₅ , a high dielectric constant with respect to high frequencies, a low dielectric loss, and a dielectric with a low temperature coefficient of resonance frequency. The characteristics are obtained. At the same time, a material that is satisfactory for use as a resonator or circuit board material can be obtained, and at the same time, downsizing can be achieved.

Claims (1)

(57) [Claims] 1. A dielectric ceramic composition having a composition formula of Ba Sm _1/2 (Nb _x Ta _1-x ) _1/2 O _{3 with} 0 ≦ x ≦ 1.