JP3460234B2 - Dielectric porcelain composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic, and more particularly to a dielectric resonator used in a high frequency region such as a microwave and a millimeter wave band, a dielectric ceramic used for a dielectric filter and the like.

[0002]

2. Description of the Related Art In recent years, dielectric ceramics have been widely used for dielectric resonators, filters, etc. in the microwave and millimeter wave regions (hereinafter collectively referred to as microwaves) having wavelengths of several cm or less. The dielectric material used in such applications has a high unloaded Q (Qu) value, a large relative dielectric constant (ε _r ), and can change the temperature coefficient (τ _f ) of the resonance frequency arbitrarily. Required.

Conventionally, BaO--TiO ₂ system porcelain and ZrO ₂ --SnO ₂ --T have been used as materials suitable for such applications.
Known are iO ₂ system porcelains, porcelains in which some of them are replaced with other elements, BaO—SrO—NiO—Nb ₂ O ₅ system porcelain, and the like.

[0004]

However, the conventional materials have various problems such as a low unloaded Q value and a low relative dielectric constant. In particular, a dielectric material having a high unloaded Q value has been strongly demanded with the recent increase in communication frequency.

An object of the present invention is to provide a dielectric ceramic having a high unloaded Q value and a large relative dielectric constant.

[0006]

In the present invention, the composition formula is Ba
When represented by _x (Co _y Ta _z ) O _n (n is an arbitrary number),
The composition of the components is x + y + z = 1 in molar fraction and 0.470.
≤ x ≤ 0.499, 0.155 ≤ y ≤ 0.166, 0.
The conventional problems are overcome by the dielectric ceramic composition in the range of 334 ≦ z ≦ 0.375.

[0007]

The composition formula is Ba _x (Co _y Ta _z ) O _n (however, x +
In the dielectric ceramic composition represented by y + z = 1),
If x is larger than 0.499, no sintering is performed or the unloaded Q value is low, and if x is smaller than 0.470, the unloaded Q value is low. When y is larger than 0.166, the unloaded Q value is low, and when y is smaller than 0.155, the temperature coefficient of the resonance frequency is too large on the negative side and the unloaded Q value is low. Therefore, in the composition range of the present invention, a dielectric ceramic having a high unloaded Q value and a large relative permittivity can be obtained.

[0008]

EXAMPLES As the starting material for the dielectric porcelain in the present invention, any of the component element oxides, carbonates, hydroxides, alkoxides and the like may be used.

The raw material powders can be mixed by a wet mixing method in which they are mixed with water or an organic solvent in a ball mill,
A dry mixing method or the like in which the materials are mixed in a mixer or the like and used in a ball mill without using a solvent is generally used, and any method may be used. Alternatively, an alkoxide method or a coprecipitation method may be used. Since the process is relatively complicated and it is easy to obtain a homogeneous mixture, the method of mixing in a ball mill using a solvent is desirable.Furthermore, a dispersant is used to improve the dispersibility of the powder, and PH adjustment is required. You can go.

The mixture need not be calcined, but the calcining can shorten the firing time. As a method for pulverizing the calcined product or the mixture, there is a method using a ball mill, a high-speed rotary pulverizer, a medium stirring mill, an air flow pulverizer, or the like.
Either may be used.

Examples will be shown below. Chemically highly pure BaCO ₃ , CoO, and Ta ₂ O ₅ were used as starting materials, and these were weighed so as to have a predetermined composition, and wet-mixed with ethanol using a ball mill. The mixture was removed from the ball mill and dried, then dried in air at 100
It was calcined at a temperature of 0 ° C. for 2 hours.

The calcined product was wet-ground in the above ball mill together with ethanol. After removing the crushed mud from the ball mill and drying it, the powder has a concentration of 6% as a binder.
8% by weight of the above polyvinyl alcohol solution was added and mixed to homogenize, and the mixture was sized through a 32 mesh sieve.
For the sized powder, the molding pressure is 1 ton using the mold and hydraulic press.
A circular plate having a diameter of 7 mm and a thickness of about 3 mm was formed at a pressure of / cm ² .

The molded body was placed in a high-purity magnesia pod and held in air at a temperature of 1600 ° C. for 1 to 100 hours for firing to obtain a dielectric ceramic composition.

From the measurement by the conductor cavity type dielectric cylinder resonator method, the resonance frequency, the no-load Q (Q _u ) value and the relative permittivity (ε _r )
I asked. The temperature coefficient (τ _f ) of the resonance frequency is -50 ℃ ~
It was determined in the range of 50 ° C. The resonance frequency is 10.5-11.
It was in the range of 5 GHz.

The relative permittivity, resonance frequency (ppm / ° C.) and unloaded Q value thus obtained are shown in (Table 1). In Table 1, those marked with * are comparative examples outside the scope of the present invention.

[0016]

[Table 1]

As is clear from the results shown in (Table 1),
The dielectric ceramic composition within the composition range of the present invention has a high unloaded Q value while maintaining a large relative dielectric constant in the microwave frequency band. Moreover, the temperature coefficient of the resonance frequency is in a wide range from about -20 ppm / ° C to around 0. Therefore, the dielectric ceramic composition of the present invention is useful, for example, for constructing a low-loss filter, a resonator, or the like.

The reason for limiting the composition range of the present invention is as follows. When x becomes larger than 0.499, sample 1
Or the unloaded Q value becomes low as in Sample 2 and Sample 4 and Sample 5, which does not meet the object of the present invention. When x is smaller than 0.470, sample 1
As shown in No. 9, the unloaded Q value becomes low.

When y is larger than 0.166, sample 2
And the unloaded Q value is low as in Sample 9, and y is 0.1.
When it is smaller than 55, the temperature coefficient of the resonance frequency becomes too large on the negative side and the unloaded Q as in Samples 8 and 13.
The value is too low to meet the purpose of the invention.

Further, zirconium oxide is added as a sub-component, and converted to a zirconium component to 0.01 to 0.01% of the main component.
0.70 wt. % Was added. As shown in (Table 1), the zirconium component is 0.50 wt. %, The unloaded Q value can be improved, but the amount of zirconium added is 0.50w of the main component.
t. When it is more than%, the unloaded Q value is deteriorated as in Sample 25. However, the characteristics of sample 25 were also better than those of the conventional dielectric ceramic composition.

[0021] Incidentally, can improve sinterability by the addition of small additives, properties are not a greatly degraded. For example, for sample 6 A
0.05wt the l ₂ O _3. %, The firing temperature is lowered by about 100 ° C., and ZnO is added at 0.02 wt. %, The firing temperature was lowered by about 50 ° C., but the characteristics did not change significantly in either case. Similar effects can be expected by using other additives.

[0022]

According to the present invention, the composition formula is expressed as Ba _x (Co _y T
_az ) O _n (n is an arbitrary number), the component composition is x + y + z = 1 in mole fraction and 0.470 ≦ x ≦ 0.
499, 0.155 ≦ y ≦ 0.166, 0.334 ≦ z
Since the dielectric ceramic composition is in the range of ≦ 0.375, a dielectric ceramic having a high unloaded Q value and a large relative dielectric constant can be obtained. Further, the temperature coefficient of the resonance frequency can be finely changed according to the composition.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 61-8804 (JP, A) JP-A 61-142601 (JP, A) JP-A 1-123488 (JP, A) JP-A 3- 5357 (JP, A) JP-A-3-171507 (JP, A) JP-A-4-331761 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 3/12 312 C04B 35/495 H01P 7/10

Claims (2)

(57) [Claims] 1. When the composition formula is expressed by Ba _x (Co _y Ta _z ) O _n (n is an arbitrary number) x + y + z = 1 0.470 ≦ x ≦ 0.499 0.155 ≦ y ≦ 0.166 A dielectric ceramic composition comprising an oxide of a component in the range of 0.334 ≦ z ≦ 0.375. 2. A composition containing Ba _x (Co _y Ta _z ) O _n as a main component and a zirconium component as a sub-component of 0.01 to 0.
The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition is contained in an amount of 70 % by weight.