JPH07114823A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composition in which no load Q is large and temperature coefficient of resonance frequency tauf shows negative change. CONSTITUTION:A dielectric ceramic composition has a composition of zinc, magnesium, niobium, and oxygen represented by the composition formula of x(Zn1-z.Mgz)O.yNb2O5 (wherein 0.4<=x<=0.55, x+y=1.00, and 0<z<=1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition containing zinc, magnesium, niobium and oxygen, which is suitable as a dielectric resonator material. The dielectric ceramic composition of the present invention is applied to, for example, a microwave IC substrate, a dielectric adjusting rod, etc., in addition to the dielectric resonator material.

[0002]

2. Description of the Related Art In recent years, with the integration of microwave circuits, a compact and high-performance dielectric resonator is required. The dielectric ceramic composition used for such a dielectric resonator has a large relative permittivity (ε _r ), and
It is required that the stability of the temperature coefficient (τ _f ) of the resonance frequency and the linearity of the temperature characteristic of the resonance frequency be excellent and that the unloaded Q be large.

As such a dielectric porcelain composition, a composition containing TiO ₂ , BaO-TiO ₂ or the like as a main component has been conventionally known, but it has a large temperature coefficient and a dielectric loss in the microwave band. It is too big to be put to practical use. In addition, (CaO) _x · (ZnO) _y
Although there is a proposal (Japanese Patent Publication No. 5-803) regarding a (Nb ₂ O ₅ ) _z based dielectric ceramic composition, a sufficiently large Q value has not been obtained.

[0004]

An object of the present invention is to provide a dielectric ceramic composition suitable as a dielectric resonator material. Another object of the present invention is to provide a dielectric ceramic composition having a large unloaded Q and a negative change in the temperature coefficient (τ _f ) of the resonance frequency.

[0005]

Among the many constituent elements used in dielectric porcelain compositions, the inventors have found that a particular porcelain composition consisting of a combination of zinc, magnesium, niobium and oxygen. It was found that the above object can be achieved by the above. The present invention provides a compositional formula, x (Zn _1-Z · Mg _Z ).
O · yNb ₂ O ₅ (wherein 0.4 ≦ x ≦ 0.55, x +
y = 1.00 and 0 <Z ≦ 1. ) Zinc represented by
It relates to a dielectric ceramic composition composed of magnesium, niobium and oxygen.

The dielectric ceramic composition of the present invention is characterized by a very large unloaded Q and a negative temperature coefficient τ _f of the resonance frequency. As a result, it becomes possible to control the characteristics by using together with a dielectric ceramic having a large temperature coefficient, which has been difficult to put into practical use. In the present invention, x in the composition formula
When the mole fraction of is less than 0.4 or greater than 0.55, the unloaded Q becomes small, so ZnO, MgO
The mole fractions of Nb ₂ O ₅ and Nb ₂ O ₅ are limited to the above range.

An example of a suitable method for producing the dielectric ceramic composition of the present invention will be described below. Zinc oxide, magnesium oxide,
Each predetermined amount of niobium oxide is wet mixed with a solvent such as water or alcohol. Then, after removing water, alcohol, etc., it is pulverized and calcined in an oxygen-containing gas atmosphere (for example, an air atmosphere) at 900 to 1100 ° C. for about 2 hours. The calcined material thus obtained is crushed, mixed with an organic binder such as polyvinyl alcohol to homogenize, dried and crushed, and pressure-molded (pressure 100 to 100).
0 kg / cm ² ). As the molding method, in addition to uniaxial pressure molding, HIP, doctor molding, cast molding and the like may be used. The dielectric ceramic composition represented by the above composition formula is obtained by firing the obtained molded product at 1200 to 1400 ° C. in an oxygen-containing gas atmosphere such as air.

The thus-obtained dielectric ceramic composition is used as it is or by being processed into a suitable shape and size as required, to thereby form a dielectric resonator, a dielectric substrate for microwave IC, a dielectric. It can be used as a material for adjusting rods and the like, and particularly when used as a dielectric resonator used in the microwave band, an excellent effect is exhibited.

As raw materials for zinc, magnesium and niobium, besides carbonates such as ZnO, MgO and Nb ₂ O ₅ , it is possible to use carbonates and hydroxides which become oxides during firing.

[0010]

EXAMPLES The present invention will be described more specifically by showing Examples and Comparative Examples below. Example 1 0.5 mol of magnesium oxide (MgO) powder and 0.5 mol of niobium oxide (Nb ₂ O ₅ ) powder were put in a ball mill together with ethanol and wet-mixed for 12 hours. The mixture was taken out of the ball mill, the solvent ethanol was evaporated, and the mixture was crushed for 1 hour on a muller. The crushed product was calcined at 1000 ° C. in an air atmosphere, and then crushed again for 1 hour with a raider to obtain a calcined powder.

Then, an appropriate amount of polyvinyl alcohol solution was added to the calcined powder and mixed uniformly, and then the diameter was 15 mm.
A pellet having a φ and a thickness of 5.5 mm was formed, fired in an air atmosphere at 1250 ° C. for 2 hours and sintered to obtain a dielectric ceramic composition of the present invention. The porcelain composition thus obtained was cut into an appropriate size and then measured by a dielectric resonance method to obtain an unloaded Q and a relative permittivity ε _r at a resonance frequency f ₀ (3 to 6 GHz). The temperature dependence of the resonance frequency was measured in the range of -40 to 50 ° C to obtain the temperature coefficient τ _f . The results are shown in Table 1.

Examples 2 to 4 Dielectric ceramic compositions were produced in the same manner as in Example 1 except that the mixing ratio of zinc oxide, magnesium oxide and niobium oxide in Example 1 was changed as shown in Table 1. Then, the characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 1 to 4 Dielectric porcelain compositions were produced in the same manner as in Example 1 except that the amounts of the starting materials used were changed so that the dielectric porcelain compositions had the compositions shown in Table 1. The electrical properties were measured. The results are shown in Table 1.

[0014]

[Table 1]

[0015]

The dielectric ceramic composition of the present invention has an unloaded Q value.
Has a relatively large relative dielectric constant and a negative temperature coefficient. Therefore, it becomes possible to control the characteristics in combination with a dielectric ceramic having a large temperature coefficient, which has been difficult to put into practical use, and it is suitable as a dielectric ceramic material.

Claims (1)

[Claims] 1. A composition _{formula, x (Zn 1-Z ·} Mg Z) O ·
yNb ₂ O ₅ (wherein 0.4 ≦ x ≦ 0.55, x + y =
1.00 and 0 <Z ≦ 1. ) A dielectric ceramic composition composed of zinc, magnesium, niobium and oxygen represented by the formula: