JPH05298922A - Dielectric ceramic for microwave - Google Patents

Abstract

PURPOSE:To provide an extremely high no load Q value to a dielectric ceramic even if the ceramic has a composition with which the specific dielectric constant is high and the temperature coefficient of resonance frequency becomes near 0ppm/ deg.C by limiting the mole ratio X of a specified composition in a range; 0.3<=X<=0.8. CONSTITUTION:A ceramic is composed of barium oxide (BaO), cobalt oxide (CoO), strontium oxide (SrO), zinc oxide (ZnO), and niobium oxide (Nb2O5). The composition is defined as (1-X)Ba(Co1/3Nb2/3)O3+XSr(Zn1/3Nb2/3)O3 and the mole ratio X is limited in a range; 0.3<=X<=0.8. The ceramic has extremely high no load Q value even if the ceramic has the composition with which the specific dielectric constant becomes high and the temperature coefficient of resonance frequency becomes near 0ppm/ deg.C by compounding Ba(Co1/3Nb2/3)O3 and Sr(Zn1/3Nb2/3)O3. Consequently, on the conditions of high specific dielectric constant and no load Q value, the temperature coefficient of resonance frequency can be changed. As a result, a dielectric resonator for microwaves can be made compact and the dielectric loss is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic for microwaves, and in particular, it has a large relative permittivity (ε _r ) and a very large unloaded Q (Q _u ) and changes its composition. Therefore, the temperature coefficient (τ _f ) of the resonance frequency is 0
The present invention relates to a dielectric ceramic for microwaves, which can be changed to an arbitrary positive or negative value around ppm / ° C.

[0002]

2. Description of the Related Art In recent years, a large number of microwave dielectric resonators and dielectric filters have been used in automobile telephones and satellite broadcast receivers. Dielectric materials used for such applications have large relative permittivity (ε _r ) and no-load Q (Q _u ), and the temperature coefficient (τ _f ) of resonance frequency is 0 ppm / ° C by changing the composition. There is a demand for a device that can be set to an arbitrary positive or negative value around the center of.
Conventionally, as such a dielectric ceramic, BaO-
There were TiO ₂ series, ZrO ₂ —SnO—TiO ₂ series, and the like.

[0003]

However, in the above-mentioned conventional dielectric ceramics, when the temperature coefficient (τ _f ) of the resonance frequency shows a value near 0 ppm / ° C., the relative dielectric constant (ε _r ) is Although the value is large and satisfactory, the unloaded Q (Q _u ) cannot be said to be sufficiently large. Therefore, an apparatus incorporating a device using these materials has disadvantages such as a large loss in transmission and reception, and cannot be said to have sufficiently satisfactory characteristics.

Therefore, the present invention has been made in order to improve these, and has a composition having a large relative permittivity (ε _r ) and a temperature coefficient (τ _f ) of the resonance frequency of around 0 ppm / ° C. It is an object of the present invention to provide a dielectric ceramic for microwaves which has a very large value of unloaded Q (Q _u ) even in the ratio.

[0005]

In order to achieve the above object, the present invention provides barium oxide (BaO), cobalt oxide (CoO), strontium oxide (SrO), zinc oxide (ZnO), niobium oxide (Nb ₂ O). ₅ ) ceramics whose composition formula is (1-X) Ba (Co _1/3 Nb _2/3 ) O ₃ + XSr (Zn _1/3 Nb _2/3 ) O ₃ formula (1) The value of X is in the range of 0.3 ≦ X ≦ 0.8, which is a dielectric ceramic for microwaves.

Here, Sr (Zn for all compositions_1/3N
b_2/3) O₃Limiting the molar ratio X of 0.3 ≦ X ≦ 0.8
The reason is that when X <0.3, the temperature coefficient of the resonance frequency is
(Τ _f) Becomes too large and X> 0.8,
Resonance frequency temperature coefficient (τ_f) Becomes too negative
Together with no load Q (Q_u) Becomes smaller and does not meet the demand
This is because

[0007]

As described above, according to the present invention, by using the composition of the dielectric ceramics represented by the above formula (1), the relative dielectric constant (ε _r ) is large and the temperature coefficient (τ _f ) of the resonance frequency is large. Can be a dielectric ceramic for microwaves having a very large value of unloaded Q (Q _u ) even with a composition ratio of about 0 ppm / ° C.

[0008]

Embodiment 1 An embodiment of the present invention will be described in detail below.
It The starting material is chemically pure barium carbonate (Ba).
CO₃), Cobalt oxide (CoO), niobium oxide (Nb)
₂O _Five), Strontium carbonate (SrCO₃), Suboxide
By changing the compounding ratio of lead (ZnO), 9 shown in Table 1 below.
The thing of the compounding ratio of the kind was used.

[0009]

[Table 1]

No. 1 shown in Table 1 1-No. Dielectric ceramics were each manufactured by the following manufacturing method using the compound of 9. Accurately weighed and adjusted to the composition shown in Table 1, the compounded mixture was put in a plastic pot mill, and mixed with pure water using zirconia balls for 20 hours. The mixture was dehydrated, dried, and then calcined in a magnesia container in air at a temperature of 1200 ° C. for 3 hours. This calcined product was wet pulverized in the same manner as in the above mixing step, then dehydrated and dried to obtain fine particle powder.
A binder was added to this powder and mixed sufficiently with the powder to obtain a granulated powder.

This granulated powder is molded with a mold and a hydraulic press at a molding pressure of 1 to ² t / cm ² , a diameter of 20 mm and a thickness of 12 m.
A disk-shaped molded body of m was prepared. The molded body thus obtained is put into a magnesia pod, and 1350 to 1
The dielectric ceramics were obtained by firing in air at a temperature of 500 ° C. for 24 hours. The above method is carried out using barium carbonate (Ba
CO ₃ ), cobalt oxide (CoO), niobium oxide (Nb)
₂ O ₅ ), strontium carbonate (SrCO ₃ ) and zinc oxide (ZnO) are all mixed at the same time from the beginning to explain a method for producing a dielectric ceramic.

In contrast to the above method, barium carbonate (BaC
O₃), Cobalt oxide (CoO), niobium oxide (Nb)₂
O_Five) Is used to calcinate [Ba (Co_1/3
Nb _2/3) O₃], And strontium carbonate (SrC
O₃), Zinc oxide (ZnO), niobium oxide (Nb)
₂O_Five) Calcined product [Sr (Zn
_1/3Nb_{2 / 3}) O₃] And are mixed in the ratio shown in Table 2 below.
Pulverize, then granulate, mold and fire by the above method to obtain a dielectric
Even if ceramics are obtained, the same result as the above method can be obtained.
It

That is, the fired body fired by the above two manufacturing methods has Ba (Co _1/3 Nb _2/3 ) O ₃ and Sr (Z) which are composite perovskite structures in any case.
crystals _{n 1/3 Nb 2/3) O} 3 is one that is complex.
After polishing both surfaces of the fired dielectric ceramics and the outer diameter so that the resonance frequency was about 5 GHz, the dielectric characteristics were measured by the following method. The relative permittivity (ε _r ) and unloaded Q (Q _u ) of the dielectric ceramics were measured by the Hacky-Coleman method. The temperature coefficient (τ _f ) of the resonance frequency is the resonance frequency f (2
0) as a reference, the resonance frequencies f (-40) and f (80) at temperatures of -40 ° C and + 80 ° C and the temperature difference ΔT [here, ΔT = (+ 80 ° C)-(-40 ° C)
= 120 ° C.] was calculated according to the following equation (2).

Τ _f = {f (80) −f (−40)} / {f (20) × 120} Formula (2) No. shown in Table 1 above. 1-No. Table 2 below shows the measurement results of the dielectric properties of the dielectric ceramics manufactured from the compound of No. 9.

[0015]

[Table 2]

The sample numbers marked with * are shown here. 1 and No. No. 9 is a comparative example outside the scope of the present invention, and other sample Nos. 2 to No. 8 is an embodiment within the scope of the present invention. According to the results shown in Table 2, Sr (Zn _1/3 Nb
_2/3 ) When the molar ratio of O ₃ is in the range of 0.3 to 0.8, the relative permittivity (ε _r ) and the unloaded Q (Q _u ) are large, and the temperature coefficient (τ) of the resonance frequency is _It can be seen that _f ) shows a positive or negative value not too large around 0 ppm / ° C.

[0017]

As described in detail above, the dielectric ceramics for microwaves according to the present invention is Ba (Co _1/3).
By combining Nb _2/3 ) O ₃ and Sr (Zn _1/3 Nb _2/3 ) O ₃ , the relative dielectric constant (ε _r ) is large and the temperature coefficient (τ _f ) of the resonance frequency is 0 ppm / ° C. The unloaded Q (Q _u ) has a very large value even at a composition ratio that is set to be near. Therefore, the relative permittivity (ε _r ) and unloaded Q
Since the temperature coefficient (τ _f ) of the resonance frequency can be changed under the condition that (Q _u ) is large, miniaturization of the microwave dielectric resonator and the like and reduction of loss can be achieved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hosaku Sato 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A ceramic comprising barium oxide (BaO), cobalt oxide (CoO), strontium oxide (SrO), zinc oxide (ZnO), and niobium oxide (Nb ₂ O ₅ ), the composition formula of which is (1) -X) Ba (Co _1/3 Nb _2/3 ) O ₃ + XSr (Zn _1/3 Nb _2/3 ) O ₃ and the value of X is 0.3 ≦ X ≦ 0.8. A dielectric ceramic for microwaves, which is characterized in that