JP2872438B2 - 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 composition composed of barium, titanium, samarium and oxygen, which is suitable as a dielectric resonator material. The dielectric ceramic composition of the present invention can be used for, for example, a substrate for a microwave IC, a dielectric adjustment material, and the like, in addition to the dielectric resonator material.

[0002]

2. Description of the Related Art In recent years, with the integration of microwave circuits, a small and high-performance dielectric resonator has been demanded. The dielectric ceramic composition used for such a dielectric resonator has a large relative permittivity ε _r , a stability of the temperature coefficient τ _f of the resonance frequency, and a linearity of the temperature characteristic of the resonance frequency. There are demands for excellent characteristics such as high unloaded Q.

Conventionally, such a dielectric porcelain composition has been
Although those containing TiO ₂ , BaO—TiO ₂ or the like as a main component are known, there are aspects that are difficult to put into practical use due to a large temperature coefficient and a large dielectric loss in a microwave band. Further, proposals for _BaO-TiO 2 _-Sm 2 _{O 3} based dielectric ceramic composition (JP-B 59-375
No. 26), but a sufficiently large Q value has not been obtained.

Further, Ba (Mg _1/3 Ta _2/3 ) O ₃
System, Ba (Zn _1/3 Ta _2/3 ) O ₃ system, Ba (Zn
Dielectric porcelain compositions having a perovskite structure, such as _1/3 Nb _2/3 ) O _3, are also known. Is too large.

[0005]

An object of the present invention is to provide a dielectric ceramic composition suitable as a dielectric resonator material, particularly a dielectric resonator material used in the 0.1 to 4 GHz band. Another object of the present invention is to provide a dielectric ceramic composition having a high dielectric constant, a large Q, and a good stability of τ _f .

[0006]

SUMMARY OF THE INVENTION The present inventors have developed, among a number of component elements used in a dielectric porcelain composition, a specific porcelain composition comprising a combination of barium, titanium, samarium and oxygen. It has been found that the above object can be achieved. The present invention relates to the composition formula xBaO.yTiO ₂ .z
Sm ₂ O ₃ (wherein, 0.15 ≦ x ≦ 0.25, 0.725
<Y ≦ 0.85, 0 <z ≦ 0.018, x + y + z =
It is one. The present invention relates to a dielectric porcelain composition comprising barium, titanium, samarium and oxygen represented by the following formula:

Since the dielectric ceramic composition of the present invention has a large relative dielectric constant, the resonator can be miniaturized, and the unloaded Q also increases. Further, the temperature coefficient τ _f of the resonance frequency is small. In the present invention, when the mole fraction of BaO is larger than 0.25 or the mole fraction of TiO ₂ is smaller than 0.725, the temperature coefficient τ _f of the resonance frequency increases,
The molar fractions of aO and TiO ₂ are limited to the above range. When the mole fraction of Sm ₂ O ₃ is larger than 0.018, the no-load Q becomes small, so the mole fraction of Sm ₂ O ₃ is limited to the above range. According to the present invention, since the content of samarium oxide is small, it can be manufactured at low cost.

An example of a preferred method for producing the dielectric ceramic composition of the present invention will be described below. The starting materials of barium carbonate, titanium oxide, and samarium oxide are wet-mixed in predetermined amounts with a solvent such as water or alcohol. Subsequently, after removing water, alcohol and the like, the mixture 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 product thus formed is pulverized, mixed with an organic binder such as polyvinyl alcohol to homogenize, dried, pulverized, and pressure-molded (pressure 100 to 1).
000 kg / cm ² ). Then, when this molded product is fired at 1200 to 1400 ° C. in an oxygen-containing gas atmosphere such as air, the dielectric ceramic composition represented by the above composition formula is obtained.

The dielectric ceramic composition thus obtained can be processed as it is or as needed in an appropriate shape and size to obtain a dielectric resonator, a dielectric substrate for microwave IC, a dielectric adjustment rod. And the like. Particularly, when a dielectric resonator used in the 0.1 to 4 GHz band is used, an excellent effect is obtained.

The raw materials of barium, titanium, and samarium include BaCO ₃ , BaO, TiO ₂ , Sm ₂ O
_In addition to _3, etc., carbonates, hydroxides, and the like that become oxides during firing can be used.

[0011]

The present invention will be described more specifically with reference to the following examples. Example 1 0.205 mol of barium carbonate (BaCO ₃ ) powder, 0.78 mol of titanium oxide (TiO ₂ ) powder, and 0.015 mol of samarium oxide (Sm ₂ O ₃ ) powder were put into a ball mill together with ethanol, and wet-processed for 12 hours. Mixed. The mixture was taken out of the ball mill, the ethanol of the solvent was evaporated, and the mixture was pulverized for 1 hour using a crusher. The pulverized material was calcined at 950 ° C. in an air atmosphere and then pulverized again with a crusher for one hour to obtain 0.205 BaO.0.78 TiO ₂ .0.015.
A calcined powder having a composition of Sm ₂ O ₃ was obtained.

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

Examples 2 to 9 A dielectric ceramic composition was manufactured in the same manner as in Example 1 except that the mixing ratio of barium carbonate, titanium oxide and samarium oxide was changed as shown in Table 1. The characteristics were measured in the same manner as in Example 1. Table 1 shows the results. Those marked with * in the table are comparative examples outside the scope of the present invention.

[0014]

[Table 1]

[0015]

According to the present invention, a dielectric ceramic composition having a high dielectric constant, a large Q, and a good stability of τ _f can be obtained.

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Claims (1)

(57) [Claims] 1. A composition formula xBaO · yTiO ₂ · zSm ₂ O
₃ (where, 0.15 ≦ x ≦ 0.25, 0.725 <y ≦
0.85, 0 <z ≦ 0.018 , and x + y + z = 1. A) a dielectric ceramic composition comprising barium, titanium, samarium and oxygen.