JPH06325621A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composion with large dielectric constant, large no-load Q value, and small temperature variation in resonance frequency. CONSTITUTION:1.0wt.% or less lithium calculated in terms of the oxide is contained in an oxide represented by a composition formula of (Ba1-xPbx)(Nd1-y-zSmyBiz)2+ATi4+BO12+3A/2+2B (wherein 0.01<=x<=0.4, 0<=y<=0.8, 0.1<=z<=0.4, -0.5<=A<=+0.5, -0.5<=B<=+0.5, and 0.1<=y+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 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 provides a composition formula,
(Ba_1-xPb_x) (Nd_1-yzSm_yBi_z)_{2 + A}T
i _{4 + B}O_{12 + 3A / 2 + 2B}(Wherein 0.01 ≦ x ≦ 0.4, 0
≦ y ≦ 0.8, 0.1 ≦ z ≦ 0.4, −0.5 ≦ A ≦ +
0.5, −0.5 ≦ B ≦ + 0.5, but 0.1 ≦ y +
In the oxide represented by z ≦ 1), Li in terms of oxide is 1.
Dielectric porcelain set characterized by containing 0% by weight or less
Regarding the product.

According to the invention, by substituting part of Ba with Pb in the BaNd ₂ Ti ₄ O ₁₂ structure,
The permittivity can be increased and the temperature coefficient of resonance frequency can be reduced. If the replacement amount becomes too large, the Q value will decrease, so the replacement amount x is set within the above range.

Further, by substituting a part or all of Nd with Sm, it is possible to reduce the temperature change of the resonance frequency while maintaining a large dielectric constant. Furthermore, a part of Nd is B
The dielectric constant can be further increased by substituting with i,
Although the change in the resonance frequency with temperature can be reduced, the Q value decreases as the Nd substitution amount increases, so the substitution amount z is set within the above range.

Further, the composition formula, (Ba_1-xPb_x) (N
d_1-yzSm_yBi_z)_{2 + A}Ti_{4+ B}O_{12 + 3A / 2 + 2B}To
, −0.5 ≦ A ≦ + 0.5, −0.5 ≦ B ≦ + 0.
If it deviates from the range of 5, BaNd₂Ti_FourO₁₂Basic structure
It is easy to form a different phase other than structure, dielectric constant, resonance frequency
One of the temperature coefficient of Q, Q value, or more than two
The characteristics deteriorate. If it deviates from this range, Pb and B
i becomes easy to separate during firing, and the amount of separation
Is not stable, and variations in electrical characteristics easily occur, which is preferable.
Not good. In addition, when A = 0 and B = 0, that is, Ba
Nd₂Ti_FourO ₁₂Good properties are obtained in the structure.

Furthermore, the compositional formula: (Ba _1-x Pb _x )
_{(Nd 1-yz Sm y Bi} z) 2 + A Ti 4 + B O 12 + 3A / 2 + 2B
The Q value can be improved without changing the relative permittivity ε _r by including Li in the oxide represented by the following in an amount of 1.0 wt% or less in terms of oxide (Li ₂ O). If contained too much, the relative permittivity, temperature coefficient of resonance frequency, Q
Any one of the values or two or more of the characteristics are degraded.

The dielectric porcelain composition according to the present invention is prepared by mixing starting materials such as barium, lead, neodymium, samarium, bismuth and titanium carbonates and oxides which are calcined and fired to form oxides. It can be manufactured by a method of forming after firing, firing, and sintering. As Li, its oxide, nitrate or carbonate is used.

First, barium carbonate, lead oxide, 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., crushed,
900 ~ under an oxygen-containing gas atmosphere (for example, air atmosphere)
Calcination is performed at 1100 ° C. for about 1 to 5 hours. A predetermined amount of Li oxide and carbonate is added to the calcined material formed by this and pulverized by a wet or dry method, an organic binder such as polyvinyl alcohol is added, and after drying, pressure molding (pressure 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 necessary 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.

[0013]

EXAMPLES The present invention will be described more specifically by showing Examples and Comparative Examples below. Example 1 0.090 mol of barium carbonate powder (BaCO ₃ ), 0.010 mol of lead oxide powder (PbO), 0.081 mol of neodymium oxide powder (Nd ₂ O ₃ ) and bismuth oxide powder (B
i ₂ O ₃ ) 0.019 mol, and titanium oxide powder (T
0.400 mol of iO ₂ ) was put in a ball mill together 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 pulverized product was calcined at 1000 ° C in an air atmosphere, and then lithium carbonate powder (L
i ₂ CO ₃ ) was added in an amount of 0.1% by weight, the mixture was put into a ball mill again together with ethanol, and the mixture was wet-mixed for 12 hours. Then, ethanol as a solvent was evaporated, and the mixture was pulverized again with a mulcher for 1 hour. Add an appropriate amount of polyvinyl alcohol solution to this pulverized product, dry it, and form into pellets with a diameter of 9 mm and a thickness of 4 mm.
The dielectric ceramic composition of this example was obtained by firing and sintering at 1350 ° C. for 2 hours in an air atmosphere. The porcelain composition thus obtained was processed into a pellet having a diameter of about 7 mm and a thickness of about 2 mm, and then measured by a dielectric resonance method to obtain a resonance frequency (4 to 5 G).
Hz) and the unloaded Q and the relative permittivity ε _r were obtained.
Also, regarding the temperature dependence of the resonance frequency,
The temperature coefficient was measured in the range of 0 ° C. to obtain the temperature coefficient τ _f . The results are shown in Tables 1 and 2.

Examples 2 to 21 Barium carbonate powder (BaCO₃), Lead oxide powder (Pb
O), neodymium oxide powder (Nd₂O₃), Oxidized Samariu
Powder (Sm₂O₃), Bismuth oxide powder (Bi
₂O₃), And titanium oxide powder (TiO₂) Raw material
Incorporation ratio, lithium carbonate powder (Li₂CO₃) Addition amount,
And the firing temperature was changed to 1270 to 1390 ° C.
A dielectric ceramic composition was produced in the same manner as in Example 1, and the characteristics were
It was measured. The results are shown in Tables 1 to 4.

Comparative Example 1 Barium carbonate powder (BaCO ₃ ) and lead oxide powder (Pb
O), neodymium oxide powder (Nd ₂ O ₃ ), bismuth oxide powder (Bi ₂ O ₃ ), and titanium oxide powder (Ti
O ₂ ) was made to have a molar ratio as shown in Table 1, lithium carbonate powder (Li ₂ CO ₃ ) was not added, and the firing temperature was changed to 1350 ° C. A porcelain composition was manufactured and its physical properties were measured. The results are shown in Tables 1 and 2.

Comparative Examples 2 to 7 Barium carbonate powder (BaCO₃), Lead oxide powder (Pb
O), neodymium oxide powder (Nd₂O₃), Oxidized Samariu
Powder (Sm₂O₃), Bismuth oxide powder (Bi
₂O₃), And titanium oxide powder (TiO₂) Raw material
Incorporation ratio, lithium carbonate powder (Li₂CO₃) Addition amount,
And the firing temperature was changed from 1270 to 1390 ° C.
A dielectric ceramic composition was manufactured in the same manner as in Example 1, and the physical properties were measured.
Decided The results are shown in Tables 1 to 4.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

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_1-xPb_x) (Nd
_1-yzSm_yBi_z) _{2 + A}Ti_{4 + B}O_{12 + 3A / 2 + 2B}(formula
0.01 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.8, 0.1 ≦
z ≦ 0.4, −0.5 ≦ A ≦ + 0.5, −0.5 ≦ B ≦
+0.5, where 0.1 ≦ y + z ≦ 1)
Content of Li in an amount of 1.0 wt% or less in terms of oxide
A dielectric porcelain composition characterized by the above.