JPH06275126A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composition of high permittivity, large no-load Q, and of small temperature variation of resonance frequency. CONSTITUTION:A dielectric ceramic composition comprises barium, neodymium, samarium, bismuth, titanium and oxygen. The composition formula is Ba(Nd1-x-ySmxBiy)2+ATi4+BO12+3A/2+2B, (where 0<=x<=0.8, 0.2<=y<=0.5, -0.5<=A<=+0.5, -0.5<=B<=+0.5, and 0.2<=x+y<=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 suitable as a material for a dielectric resonator or the like. The dielectric ceramic composition of the present invention can be applied to, for example, a dielectric substrate for microwave IC, 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, excellent stability of the temperature coefficient τ _f of the resonance frequency and linearity of the temperature characteristic of the resonance frequency. It is required that the unloaded Q be large. As such a dielectric ceramic composition, Ti
A material containing O ₂ , MgO-CaO-TiO ₂ or the like as a main component is known, but the former has a problem that the temperature coefficient is large and the latter has a small relative dielectric constant.

As an improved system, BaO-TiO ₂ -Nd is used.
Proposal of ₂ O ₃ based dielectric ceramic composition [Ber.Dt.K
eram.Ges.55 (1978) Nr.7; JP 60-35406 Publication], _{or, BaO-TiO 2 -Nd 2 O} 3 -B
Although a proposal has been made for the i ₂ O ₃ system (Japanese Patent Laid-Open No. 62-72558), a smaller dielectric resonator is required, and therefore, development of a material having a larger dielectric constant is desired.

[0004]

An object of the present invention is to provide a dielectric ceramic composition having excellent characteristics as a microwave dielectric resonator material, particularly a high dielectric constant, a large unloaded Q, and a small change in resonance frequency with temperature. It is to provide a dielectric ceramic composition.

[0005]

The present invention is based on the composition formula, B
a (Nd _1-xy Sm _x Bi _y ) _{2 + A} Ti _{4 + B} O _{12 + 3A / 2 +
2B} (wherein 0 ≦ x ≦ 0.8, 0.2 ≦ y ≦ 0.5, −
0.5 ≤ A ≤ +0.5, -0.5 ≤ B ≤ +0.5, where 0.2 ≤ x + y ≤ 1), a dielectric porcelain composed of barium, neodymium, samarium, bismuth, titanium and oxygen. It relates to a composition.

According to the present invention, by substituting Sm for part or all of Nd in the BaNd ₂ Ti ₄ O ₁₂ structure, it is possible to reduce the temperature change of the resonance frequency while maintaining a large dielectric constant. Further, by substituting a part of Nd with Bi, the dielectric constant can be further increased and the temperature change of the resonance frequency can be reduced, but the Q value decreases when the substitution amount of Nd increases, so the substitution amount y falls within the above range. Is set.

Further, the composition formula, Ba (Nd _1-xy Sm _x
Bi _y ) _{2 + A} Ti _{4 + B} O _{12 + 3A / 2 + 2B} , -0.5
If it deviates from the ranges of ≦ A ≦ + 0.5 and −0.5 ≦ B ≦ + 0.5, it becomes easy to form a different phase other than the basic structure of BaNd ₂ Ti ₄ O ₁₂ and the dielectric constant, temperature coefficient of resonance frequency, Q
Any one of the values or two or more of the characteristics are degraded. Further, if it deviates from this range, Bi and the like are likely to be separated during firing, and the amount of separation thereof is not stable, and variations in electrical characteristics are likely to occur, which is not preferable. In addition, A
= 0 and B = 0, that is, good characteristics are obtained in the BaNd ₂ Ti ₄ O ₁₂ structure.

The dielectric ceramic composition according to the present invention is calcined by mixing starting materials such as barium, neodymium, samarium, bismuth and titanium carbonates and oxides, which are calcined and calcined to form oxides. After that, it can be manufactured by a method of molding, firing and sintering.

First, barium carbonate, neodymium oxide, samarium oxide, bismuth oxide, and titanium 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 is performed at ℃ for about 1 to 5 hours. The calcined product thus formed is pulverized by a wet or dry method, an organic binder such as polyvinyl alcohol is added, dried and then pressure-molded (pressure of about 100 to 1000 kg / cm ² ). The molding method may be uniaxial pressure molding, HIP, doctor molding, cast molding, or the like. The above-mentioned dielectric ceramic composition is obtained by firing the obtained molded body at 1200 to 1400 ° C. in an oxygen-containing gas atmosphere such as air.

The dielectric ceramic composition thus obtained may be used as it is or by being processed into an appropriate shape and size as required to prepare a dielectric resonator, a dielectric substrate for microwave IC, a dielectric adjusting rod, or the like. It can be used as a material, and particularly when used in the MHz to GHz band, excellent effects are exhibited.

[0011]

EXAMPLES The present invention will be described more specifically by showing Examples and Comparative Examples below. Example 1 barium carbonate powder (BaCO ₃₎ 0.100 mol, neodymium oxide powder (Nd ₂ O ₃₎ 0.075 mol, bismuth oxide powder (Bi ₂ O ₃₎ 0.025 mol, and titanium oxide powder (TiO ₂ ) 0.400 mol was placed in a ball mill with ethanol and wet mixed for 12 hours. The solvent ethanol was evaporated and the mixture was crushed for 1 hour with a mulcher. The crushed product was calcined at 1000 ° C. in an air atmosphere and then crushed again for 1 hour with a mashing machine. An appropriate amount of polyvinyl alcohol solution was added to this pulverized product and dried, then the diameter was about 9 mm and the thickness was 4 mm.
Of the dielectric ceramic composition Ba (N) of the present embodiment.
d _0.81 Bi _0.19 ) ₂ Ti ₄ O ₁₂ was obtained. The porcelain composition thus obtained was processed into pellets having a diameter of about 7 mm and a thickness of about 2 mm, and then measured by the dielectric resonance method to determine the resonance frequency (4
Up to 5 GHz), the unloaded Q and the relative permittivity ε _r were determined. Regarding the temperature dependence of the resonance frequency, 0 ° C
To 50 ° C., the temperature coefficient τ _f was determined. The results are shown in Tables 1 and 2.

Examples 2 to 21 Barium carbonate powder (BaCO ₃ ), neodymium oxide powder (Nd ₂ O ₃ ), samarium oxide powder (Sm ₂ O ₃ ),
The raw material charging ratio of the bismuth oxide powder (Bi ₂ O ₃ ) and the titanium oxide powder (TiO ₂ ) and the firing temperature were set to 125.
A dielectric ceramic composition was produced in the same manner as in Example 1 except that the temperature was changed to 0 to 1350 ° C., and the characteristics were measured. The results are shown in Table 1, Table 2, Table 3 and Table 4.

Comparative Example 1 Barium carbonate powder (BaCO ₃ ), neodymium oxide powder (Nd ₂ O ₃ ) and titanium oxide powder (TiO ₂ ) were made to have a molar ratio as shown in Table 3, and the firing temperature was 1.
A dielectric ceramic composition was produced in the same manner as in Example 1 except that the temperature was changed to 350 ° C., and the physical properties were measured. The results are shown in Tables 3 and 4.

Comparative Examples 2 to 5 Barium carbonate powder (BaCO ₃ ), neodymium oxide powder (Nd ₂ O ₃ ), samarium oxide powder (Sm ₂ O ₃ ),
The raw material charging ratio of the bismuth oxide powder (Bi ₂ O ₃ ) and the titanium oxide powder (TiO ₂ ) and the firing temperature were set to 125.
A dielectric ceramic composition was produced in the same manner as in Example 1 except that the temperature was changed to 0 to 1350 ° C., and the physical properties were measured. The results are shown in Tables 3 and 4.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

INDUSTRIAL APPLICABILITY The dielectric ceramic composition of the present invention has a particularly high dielectric constant, a large no-load Q, a small change in resonance frequency with temperature, and is used in dielectric resonator materials, particularly in the MHz to GHz band. It is suitable as a resonator material. In addition to the dielectric resonator material, the dielectric ceramic composition of the present invention can be applied to, for example, a dielectric substrate for microwave IC, a dielectric adjusting rod, and the like.

Claims (1)

[Claims] 1. A composition formula, Ba (Nd_1-xySm_xBi
_y)_{2 + A}Ti_{4 + B}O _{12 + 3A / 2 + 2B}(In the formula, 0 ≦ x ≦ 0.
8, 0.2 ≦ y ≦ 0.5, −0.5 ≦ A ≦ + 0.5, −
0.5 ≦ B ≦ + 0.5, but 0.2 ≦ x + y ≦ 1)
Represented barium, neodymium, samarium, bismuth,
A dielectric ceramic composition composed of titanium and oxygen.