JPH09227225A - Dielectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain superior dielectric characteristics by forming a dielectric porcelain compsn. having a compsn. represented by a specified formula. SOLUTION: Powders of starting materials such as CaCO3 , Bi2 O3 , La2 O3 and TiO2 are blended in a prescribed ratio and wet-mixed with water in a ball mill. This mixture is dried, calcined at about 900-1,200 deg.C in the air, wet- pulverized for about >=20hr in a ball mill and dried. The resultant powdery mixture is compacted in a prescribed shape and fired at about 1,000-1,400 deg.C for about 2hr in the air to obtain the objective dielectric porcelain compsn. having a compsn. represented by the formula aCaO-bBi2 O3 -cR2 O3 -dTiO2 (where R is La, Ce, Pr, Nd, Sm, Eu or Gd, a+b+c+d=100mol%, 11.8<=a<=16.8, 14.3<=b<=31.6, 0.5<=c<=15.8 and 54.6<=d<=59.6).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric porcelain composition mainly used for microwave band communication and broadcasting equipment filters and capacitors.

[0002]

2. Description of the Related Art In recent years, due to advances in communication technology, mobile communication systems such as car phones and mobile phones such as PHS whose services have been started, GPS (Global Positioning System)
m) is rapidly spreading. For this reason, the frequency band used for communication has been expanded, and the use in the microwave band has become active.

In the old days, a cavity resonator, an antenna and the like were used in the circuit used in this microwave band.
However, since these parts have the same size as the wavelength of microwaves, they can be used in automobile phones, mobile phones, small GPs, etc.
It has not been possible to reduce the size of components that can be applied to S devices and the like.

On the other hand, in recent years, miniaturization of circuit parts has been actively carried out by using a dielectric resonator in a frequency stabilizing circuit of a microwave filter or an oscillator.

In recent years, miniaturization of mobile communication devices has progressed from the pocket size to the palm size. Therefore, the demand for miniaturization of parts used in mobile communication devices has become more remarkable.

The characteristics required of such a dielectric ceramic are that the permittivity (hereinafter referred to as εr) in the frequency band used is large, and the temperature coefficient of the resonance frequency (hereinafter referred to as | τ).
_f ) is sufficiently small, and the dielectric loss in the microwave band [called tan δ (= 1 / Q)] is small. It should be noted that the magnitude of tan δ depends on the resonance frequency f
Since it is generally expressed in the form of Q × f, this expression will be used below.

[0007] Further, the temperature compensating capacitors which have been mainly used for ICs, crystal oscillators, etc. in the past have recently been in increasing demand as bypass capacitors for digital circuits of mobile communication devices. There is.

[0008]

SUMMARY OF THE INVENTION Conventionally, for microwaves,
Alternatively, as a dielectric ceramic composition for a capacitor, B
a (Zn _1/3 , Ta _2/3 ) O ₃ system, BaO—TiO ₂ system, Z
rO ₂ -SnO ₂ -TiO ₂ system, BaO-rare earth oxide -
Materials such as TiO ₂ series and (Pb, Ca) ZrO ₃ are known.

However, in the materials having the compositions disclosed so far, there is a tendency that the larger εr is, the smaller Q × f is in the microwave band.

In order to solve the drawback, the present inventors have found that BaO--La ₂ O ₃ --Sm ₂ O ₃ --Bi ₂ O ₃ --TiO ₂
It was proposed that a porcelain composition having a sufficiently large Q × f, εr> 110, and a sufficiently small | τf | can be obtained in the system (Japanese Patent Application No. 5-275360).

However, with the spread of mobile communication, in order to further miniaturize and improve the performance of communication devices, εr, Q × f
Is desired and a material having a smaller | τf | is desired.

Therefore, the technical problem of the present invention is that εr, Q
It is an object of the present invention to provide a dielectric ceramic composition having a large xf and a sufficiently small | τf |.

[0013]

In order to solve the above problems SUMMARY OF THE INVENTION The present inventors have found that the general formula aCaO-bBi ₂ O ₃ -
cR ₂ O ₃ -dTiO ₂ (wherein R is La, Ce, Pr,
As a result of various studies focusing on the dielectric ceramics represented by at least one of Nd, Sm, Eu, and Gd), 1
1.8 ≦ a ≦ 16.8, 14.3 ≦ b ≦ 31.6, 0.5 ≦
When the molar ratio is within the range of c ≦ 15.8, 54.6 ≦ d ≦ 59.6 and a + b + c + d = 100 mol%,
It has been found that a high dielectric constant, a large Q × f, and a practically small | τf | can be obtained.

That is, in the present invention, the general formula is aCaO-b
Bi ₂ O ₃ -cR ₂ O ₃ -dTiO ₂ (where R is La, C
e, Pr, Nd, Sm, Eu, Gd) and 11.8 ≦ a ≦ 16.8, 14.3 ≦ b
≤31.6, 0.5 ≤ c ≤ 15.8, 54.6 ≤ d ≤ 59.
In the molar ratio within the range of 6, a + b + c + d = 100 mol%
The dielectric porcelain composition is characterized by

Generally, the resonance frequency f ₀ of a coaxial resonator using a dielectric ceramic is expressed by the following equation 1 when the resonance is in the TEM (λ / 4) mode.

F ₀ = c / {4L (εr) ^1/2 } (1)

Here, c is the speed of light and L is the length of the coaxial resonator. As is clear from Equation 1, L and εr are in inverse proportion to each other with respect to a certain resonance frequency f ₀ . That is, Expression 1 indicates that the use of a dielectric porcelain having a high dielectric constant can shorten the length of the coaxial resonator, which contributes to downsizing of components.

The capacitance C of the capacitor using the dielectric ceramic is expressed by the following equation 2.

C = (ε ₀ · ε _r · S) / d (2)

Here, ε ₀ is the dielectric constant of vacuum, and S and d are
These are the area and thickness of the capacitor, respectively. As is clear from Expression 2, S and εr are in inverse proportion to a certain capacity C. That is, Expression 2 shows that the use of a dielectric ceramic having a high dielectric constant can reduce the area of the capacitor, which contributes to miniaturization of parts.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on Examples.

(Example 1) First, CaCO ₃ , Bi
₂ O ₃ , La ₂ O ₃ , and TiO ₂ powders are weighed according to each composition, and then pure water is used to make a yttria-stabilized zirconia ball (hereinafter simply referred to as zirconia ball) in a resin ball mill. Wet mixing was performed for 20 hours or more to obtain a mixture. Then, the mixture is dried and then dried in the atmosphere at 9
It was calcined at a temperature of 00 to 1200 ° C. for about 4 hours to obtain a calcined product. The calcined product was wet-ground for 20 hours or more with zirconia balls and then dried. The powder obtained as described above is formed into a disk shape having a diameter of 15 mm and a thickness of about 6 mm, and is sintered in the atmosphere at a temperature of 1000 to 1400 ° C. for about 2 hours to obtain a dielectric composition shown in Table 1. A body porcelain composition was obtained.

[0023]

[Table 1]

In Table 1, the composition is aCaO-bBi.
_{2 O 3 -cLa 2 O 3 -dTiO} 2 (a, b, c and d are mol%, a + b + c + d = 100 mol%) was expressed as.

Next, εr, Q × f, and τf of the dielectric ceramics of each composition were measured by the dielectric resonator. τf
Was calculated by the following equation 3 from the difference of the resonance frequency f in the temperature range of +20 to + 60 ° C.

Τf = {f (60 ° C.) − F (20 ° C.)} / {40 × f (20 ° C.)} (3)

The measurement results are shown in Table 1 above. The resonance frequency was 2.2 to 3.8 GHz.

Example 2 CaCO ₃ , Bi ₂ O ₃ and Ce ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and in the same manner as in Example 1, a dielectric ceramic composition having the composition shown in Table 2 was obtained.

[0029]

[Table 2]

In Table 2, the composition is aCaO-b.
_{Bi 2 O 3 -cCe 2 O 3} -dTiO 2 (a, b, c and d
Is represented by mol%, a + b + c + d = 100 mol%).

Next, with respect to the dielectric porcelain having each composition, the same measurement as in Example 1 was performed, and the measurement results shown in Table 2 above were obtained.

(Example 3) CaCO ₃ , Bi ₂ O ₃ , Pr ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and in the same manner as in Example 1, a dielectric ceramic composition having the composition shown in Table 3 was obtained.

[0033]

[Table 3]

In Table 3, the composition is aCaO-b.
_{Bi 2 O 3 -cPr 2 O 3} -dTiO 2 (a, b, c and d
Is represented by mol%, a + b + c + d = 100 mol%).

Next, the same measurement as in Example 1 was carried out for the dielectric ceramics of each composition, and the measurement results shown in Table 3 above were obtained.

Example 4 CaCO ₃ , Bi ₂ O ₃ and Nd ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and a dielectric ceramic composition having a composition shown in Table 4 was obtained in the same manner as in Example 1.

[0037]

[Table 4]

In Table 4, the composition is aCaO-bBi.
_{2 O 3 -cNd 2 O 3 -dTiO} 2 (a, b, c and d are mol%, a + b + c + d = 100 mol%) was expressed as.

Next, the same measurement as in Example 1 was carried out for the dielectric ceramics of each composition, and the measurement results shown in Table 4 above were obtained.

Example 5 CaCO ₃ , Bi ₂ O ₃ and Sm ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and in the same manner as in Example 1, a dielectric ceramic composition having the composition shown in Table 5 was obtained.

[0041]

[Table 5]

In Table 5, the composition is aCaO-bBi.
₂ O ₃ -cSm ₂ O ₃ -dTiO ₂ (a, b, c and d are mol%, a + b + c + d = 100 mol%).

Next, with respect to the dielectric porcelain having each composition, the same measurement as in Example 1 was performed, and the measurement results shown in Table 5 were obtained.

Example 6 CaCO ₃ , Bi ₂ O ₃ and Eu ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and a dielectric ceramic composition having a composition shown in Table 6 was obtained in the same manner as in Example 1.

[0045]

[Table 6]

In Table 6, the composition is aCaO-bBi.
_{2 O 3 -cEu 2 O 3 -dTiO} 2 (a, b, c and d are mol%, a + b + c + d = 100 mol%) was expressed as.

Next, the same measurements as in Example 1 were carried out for the dielectric ceramics of each composition, and the measurement results shown in Table 6 were obtained.

Example 7 CaCO ₃ , Bi ₂ O ₃ and Gd ₂
Each powder of O ₃ and TiO ₂ was weighed according to each composition, and in the same manner as in Example 1, a dielectric ceramic composition having the composition shown in Table 7 was obtained.

[0049]

[Table 7]

In Table 7, the composition is aCaO-bBi.
₂ O ₃ -cGd ₂ O ₃ -dTiO ₂ (a, b, c and d are mol%, a + b + c + d = 100 mol%).

Next, the same measurements as in Example 1 were carried out for the dielectric ceramics of each composition, and the measurement results shown in Table 7 above were obtained.

As is clear from Tables 1 to 7, the general formula is aCaO-bBi ₂ O ₃ -cR ₂ O ₃ -dTiO ₂ (R is L
a, Ce, Pr, Nd, Sm, Eu, or Gd), 0.5 ≦ R ₂ O ₃ ≦
In the case of 15.8 mol%, the dielectric constant εr is 80 or more for practical use,
It shows a sufficiently large value. When R ₂ O ₃ is less than 0.5 mol%, it is difficult to obtain a sufficiently dense sintered body, and thus it is excluded from the scope of the present invention. When R ₂ O ₃ is 0.5 mol% or more, a sufficiently dense sintered body is obtained, so that the value of the dielectric constant εr increases. When R ₂ O ₃ exceeds 15.8 mol%, εr sharply decreases and falls below 80, so that it is excluded from the scope of the present invention.

In order to support further miniaturization as a mobile communication component, εr is 100 or more, that is,
More preferably, R ₂ O ₃ ≦ 12 mol%. Also, R ₂ O ₃
Regardless of the composition amount, in all composition ranges of Table 1 to Table 7,
In practice, a sufficiently large Q × f value and a sufficiently small τf have been obtained.

Further, 11.8 to 16.8 mol% of CaO and B
i ₂ O ₃ is 14.3 to 31.6 mol%, and TiO ₂ is 54.6 to
The reason why the content is 59.6 mol% is that if it is out of this range, a sufficiently dense sintered body cannot be obtained, and the dielectric properties such as εr and τf deteriorate.

[0055]

Effect of the Invention] As described above, according to the present invention, .epsilon.r, Q × f is large, | tau _f | small dielectric ceramic composition is obtained.

Claims (1)

[Claims] 1. The general formula is aCaO-bBi ₂ O ₃ -cR.
₂ O ₃ -dTiO ₂ (where R is La, Ce, Pr, N
d, Sm, Eu, at least one of Gd), 11.8 ≦ a ≦ 16.8, 14.3 ≦ b ≦ 31.6,
A dielectric porcelain composition, wherein a + b + c + d = 100 mol% at a molar ratio in the range of 0.5 ≦ c ≦ 15.8 and 54.6 ≦ d ≦ 59.6.