JPH06111623A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric ceramic in composition, which has a high dielectric constant, a large Q factor and the stabilized tauf. CONSTITUTION:Dielectric ceramic composition is composed of barium, titanium, samarium, bismuth and oxygen expressed by a composition formula xBaO.yTiO2.zSm2O3.tBiO3/2. In the formula, 0.15<=x<=0.25, 0.725<y<=0.85, 0<z<0.25, and x+y+z=1 mole, and the mole range of t is 0.001-0.1 mole relative to x+y+z=1 mole.

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 barium, titanium, samarium, bismuth and oxygen suitable as a dielectric resonator material. The dielectric ceramic composition of the present invention can be used not only as a dielectric resonator material but also as, for example, a microwave IC substrate, a dielectric adjusting rod, or the like.

[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 , stability of the temperature coefficient τ _f of the resonance frequency, and linearity of the temperature characteristic of the resonance frequency. Characteristics such as excellent and large no-load Q are required.

As such a dielectric ceramic composition,
It is known that TiO ₂ , BaO-TiO ₂ or the like is the main component, but it is difficult to put into practical use because of its large temperature coefficient and large dielectric loss in the microwave band. Further, a proposal for a BaO—TiO ₂ —Sm ₂ O ₃ -based dielectric ceramic composition (Japanese Patent Publication No. 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 system are also known, but since these have a low relative dielectric constant, they are resonators in the 0.1 to 4 GHz band, for example. Has the drawback of becoming too large.

[0005]

An object of the present invention is to provide a dielectric ceramic composition suitable as a dielectric resonator material, particularly as 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]

Among the many constituent elements used in dielectric porcelain compositions, the present inventors have found that a particular porcelain consisting of a combination of barium, titanium, samarium, bismuth and oxygen. It has been found that the above objects can be achieved by the composition. The present invention provides a composition formula xBaO · y
TiO ₂ · zSm ₂ O ₃ · tBiO _3/2 (in the formula, 0.
15 ≦ x ≦ 0.25, 0.725 <y ≦ 0.85, 0 <
z <0.025, x + y + z = 1 mol, and t is x
+ Y + z = 0.001 to 0.1 mol per 1 mol. The present invention relates to a dielectric ceramic composition composed of barium, titanium, samarium, bismuth and oxygen represented by the formula (1).

Since the dielectric ceramic composition of the present invention has a large relative permittivity, the resonator can be downsized and the unloaded Q also becomes large. Furthermore, the temperature coefficient τ _f of the resonance frequency is small. In the present invention, when the molar fraction of BaO is larger than 0.25, or the molar fraction of TiO ₂ is larger than 0.85, or the molar fraction of BaO is smaller than 0.15 or the molar fraction of TiO ₂ is small. If the rate is less than 0.725,
Since the temperature coefficient τ _f of the resonance frequency becomes large, the molar fraction of BaO and TiO ₂ is limited to the above range. Also,
And the molar fraction of Sm ₂ O ₃ is larger than 0.025, or a molar fraction of _{BiO 3/2} is greater than 0.1, since the unloaded Q is reduced, _Sm 2 _{O 3} and _{BiO 3/2}
The mole fraction of is 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. Starting materials of barium carbonate, titanium oxide, samarium oxide, and bismuth oxide are wet-mixed in predetermined amounts with a solvent such as water or alcohol. Then, after removing water, alcohol, etc., it is pulverized and then 900 to 1100 in an oxygen-containing gas atmosphere (for example, air atmosphere).
Calcination at ℃ for about 2 hours. The calcined material thus formed is pulverized, mixed with an organic binder such as polyvinyl alcohol to be homogenized, dried, pulverized, and pressure-molded (pressure 100 to 1000 kg / cm ² ). And
This molded product is exposed to an oxygen-containing gas atmosphere such as air at 120
By firing at 0 to 1400 ° C., the dielectric ceramic composition represented by the above composition formula is obtained.

The dielectric ceramic composition thus obtained is processed as it is or, if necessary, into an appropriate shape and size to obtain a dielectric resonator, a dielectric substrate for microwave IC, a dielectric adjusting rod. Etc., and particularly when used as a dielectric resonator used in the 0.1 to 4 GHz band, excellent effects are exhibited.

The raw materials for barium, titanium, samarium and bismuth are BaCO ₃ , BaO and Ti.
In addition to O ₂ , Sm ₂ O ₃ , Bi ₂ O _{3 and the} like, carbonates, hydroxides and the like which become oxides during firing can be used.

[0011]

EXAMPLES The present invention will be described more concretely with reference to the following examples. Example 1 Barium carbonate (BaCO ₃ ) powder 0.205 mol, titanium oxide (TiO ₂ ) powder 0.780 mol, samarium oxide (Sm ₂ O ₃ ) powder 0.015 mol, bismuth oxide (BiO _3/2 ) powder 0.005 was 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 pulverized with a muller for 1 hour. The pulverized product was calcined at 950 ° C. in an air atmosphere, and then pulverized again for 1 hour with a mashing machine 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 φ and a thickness of 5.5 mm was formed, fired at 1250 ° C. for 2 hours in an air atmosphere, 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 dielectric constant ε _r at a resonance frequency f ₀ (2 to 6 GHz). Regarding the temperature dependence of the resonance frequency, the temperature coefficient τ was measured in the range of -40 to 50 ° C.
_f was calculated. The results are shown in Table 1.

Examples 2 to 9 Dielectric ceramic composition in the same manner as in Example 1 except that the mixing ratio of barium carbonate, titanium oxide, samarium oxide and bismuth oxide in Example 1 was changed as shown in Table 1. Was manufactured and the characteristics were measured in the same manner as in Example 1. The results are shown in Table 1.
Shown in. 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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsushi Ueda 5 1978, Kozugushi, Ube City, Yamaguchi Prefecture Ube Kosan Co., Ltd. Ube Laboratory

Claims (1)

[Claims] 1. A composition formula: xBaO.yTiO ₂ .zS
m ₂ O ₃ · tBiO _3/2 (wherein 0.15 ≦ x ≦ 0.
25, 0.725 <y ≦ 0.85, 0 <z <0.025
And x + y + z = 1 mol, and t is 0.001 to 0.1 mol with respect to x + y + z = 1 mol. ) A dielectric ceramic composition comprising barium, titanium, samarium, bismuth and oxygen represented by