JPH107457A - Dielectric porcelain composition - Google Patents

Abstract

[PROBLEMS] To provide a dielectric ceramic composition having a temperature coefficient τ _{f of a} resonance frequency as close to zero as possible, a large Q × f value, and a large dielectric constant ε _r . SOLUTION: The dielectric ceramic composition has a general formula a · CaO.
_{-B · La 2 O 3 -c ·} TiO 2 ( where, a, b, units of c is represented by mol%, 10.0 ≦ a ≦ 25.0,1
8.0 ≦ b ≦ 34.0, 50.6 ≦ c ≦ 70.0, a +
b + c = 100 mol%), and is within the hatched area surrounded by ABCDEF in FIG.

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 communication and broadcasting equipment for a microwave band.

[0002]

2. Description of the Related Art In recent years, with the advance of communication technology, mobile communication systems such as car phones, mobile phones, PHSs,
S (Global Positioning System) 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 past, circuits used in the microwave band mainly used a cavity resonator, an antenna and the like. However, the size of these components is almost the same as the wavelength of microwaves, so that miniaturization of the components was not possible.

On the other hand, in recent years, it has become common to reduce the size of circuit components by using a dielectric resonator for a frequency stabilizing circuit of a microwave filter or a transmitter.

[0005] properties such required for dielectric materials used in the dielectric resonator, dielectric constant epsilon _r of the dielectric material in the used frequency band is large, the temperature coefficient tau _f is possible zero resonant frequency Closeness and small dielectric loss tan δ (= 1 / Q) in the microwave band. The magnitude of the dielectric loss tan δ in the microwave band is generally expressed in the form of Q × f (f is the resonance frequency at that time). Therefore, the expression of Q × f is used below.

Hitherto, Ba (Mg) has been used as a dielectric ceramic composition for microwave or temperature compensating capacitors.
_1/3 Ta _2/3 ) O ₃ system, Ba (Zn _1/3 Ta _2/3 ) O ₃
System, Ba ₂ Ti ₉ O ₂₀ system, ZrO ₂ -SnO ₂ -TiO
₂ system, BaO-rare earth-TiO ₂ system, (Pb, Ca) Z
Materials such as rO ₃ are known.

On the other hand, the frequency band used for mobile communication shifts to the high frequency side year by year and is subdivided. Characteristics required for the dielectric material of such a mobile dielectric filter used for communication while also monkey have a large epsilon _r as described above, also important to have a rather high Q × f It becomes.

[0008]

[SUMMARY OF THE INVENTION However, in the material of the composition has been previously disclosed, in the microwave band, as the Q × f is large dielectric constant epsilon _r is small, epsilon higher _r is large Q × f is There was a tendency to be small. For example, B
a × Ti = 40000-600 for a ₂ Ti ₉ O ₂₀ material
00 GHz (1 GHz conversion), but ε _r is 35-40
Ε _{r for} BaO-rare earth-TiO ₂ based materials
Although Q = 75-100, Q × f is at most about 10,000. Thus Q × f exceeds the 20000GHz, and epsilon _r is the material exceeding 40 was not present.

However, on the other hand, as described above, as the frequency band used for mobile communication is subdivided, a material having a higher Q × f and a higher ε _r is desired.

It is an object of the present invention to provide a dielectric ceramic composition having a temperature coefficient τ _f of the resonance frequency as close to zero as possible, a large Q × f value, and a large dielectric constant ε _r. is there.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors mixed CaO, La ₂ O ₃ , and TiO ₂ in an appropriate amount to synthesize a dielectric ceramic composition. It has been found that a dielectric ceramic material having a temperature coefficient τ _f of the resonance frequency close to zero, a large Q × f value, and a relatively large dielectric constant ε _r can be obtained.

That is, according to the present invention, the general formula a.CaO
−b · La ₂ O ₃ −c · TiO ₂ (however, a, b, c
Is expressed in mol%, 10.0 ≦ a ≦ 25.0,1
8.0 ≦ b ≦ 34.0, 50.6 ≦ c ≦ 70.0, a +
(b + c = 100 mol%), and a dielectric porcelain composition characterized by being within the hatched area surrounded by ABCDEF in FIG. 1 is obtained.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a triangular diagram showing the range of the dielectric ceramic composition of the present invention.

The dielectric ceramic composition of the present invention has a general formula of a
・ CaO-b ・ La ₂ O ₃ −c ・ TiO ₂ (However,
The units of a, b, and c are represented by mol%, and 10.0 ≦ a ≦ 2
5.0, 18.0 ≦ b ≦ 34.0, 50.6 ≦ c ≦ 7
0.0, a + b + c = 100 mol%).

In FIG. 1, the dielectric ceramic composition of the present invention is in a hatched area surrounded by ABCDEF. Here, when each point is represented by triangular coordinates of (a, b, c), A = (1
2.0, 18.0, 70.0), B = (25.0, 1
8.0, 57.0), C = (25.0, 24.4, 5)
0.6), D = (15.4, 34.0, 50.6), E
= (10.0, 34.0, 56.0), F = (10.
0, 20.0, 70.0).

The dielectric ceramic composition within this range has a temperature coefficient τ _{f of} resonance frequency close to zero and Q × f = 20,000 G
Hz or more, and the dielectric constant ε _r > 40.

Next, a specific example of the production of the dielectric ceramic composition according to the embodiment of the present invention will be described.

First, CaCO ₃ , La ₂ O ₃ , TiO ₂
Were weighed according to the respective compositions, and wet-mixed with pure water using zirconia balls in a resin ball mill for 20 hours to obtain a mixture. After drying this mixture, it was calcined in the atmosphere at a temperature of about 1200 ° C. for about 4 hours to obtain a calcined product. Next, the calcined product was wet-pulverized (also serving as mixing) by the ball mill, and then dried and granulated. This was formed into a disk having a diameter of 15 mm and a thickness of about 6 mm.
By sintering at a temperature of about 1600 ° C. for about 2 hours, a dielectric ceramic having the composition shown in Table 1 and FIG. 2 was obtained. Note the composition of the following Table 1, a · CaO-b · La 2 O 3 -c ·
It was represented as TiO ₂ (a + b + c = 100 mol%).

Next, the dielectric constant ε _r , the Q × f value, and the temperature coefficient τ _f of the resonance frequency were measured for the dielectric ceramics of each composition by the dielectric resonator method. Temperature coefficient of resonance frequency τ _f
Was determined from the difference of the resonance frequencies f in the temperature range of +20 to + 60 ° C. by the following equation 1.

[0021]

(Equation 1)

Table 1 shows the measurement results. In addition,
The resonance frequency was 3.0 to 4.5 GHz.

[0023]

[Table 1]

As is apparent from Table 1 above, in the composition range of CaO—La ₂ O ₃ —TiO ₂ according to the present invention,
τ _f <10 ppm / ° C., Q × f> 15000 GHz are obtained. In addition, ε _r > 40, which is a value larger than that of the existing high Q material (above, samples 1, 3, 5, 6,
7, 8, 10, 12, 14).

Generally, as a high-Q material, for example, from the viewpoint of being used as a filter for a mobile communication base station, | τ _f | <10 ppm / ° C., Q × f> 15000 GHz
Is required. However, 25 mol% of CaO
If it exceeds τ _f <10 ppm / ° C. (Comparative Sample 2), and if CaO is less than 10 mol%, a sufficiently dense sintered body cannot be obtained for practical use (Comparative Sample 11), which is excluded from the scope of the present invention. You.

When La ₂ O ₃ exceeds 34.0 mol%, Q × f <15000 GHz (Comparative Sample 1).
3) When La ₂ O ₃ is less than 18 mol%, τ _f > 10 p
pm / ° C., Q × f <15000 GHz (Comparative Sample 4) is excluded from the scope of the present invention.

When TiO ₂ exceeds 70 mol%, Q
× f <15000 GHz (Comparative Data 9), TiO
_{If 2} is less than 50.6 mol%, τ _f > 10 ppm / ° C. (Comparative Sample 15), which is excluded from the scope of the present invention.

Incidentally, as a high Q material, Q × f> 2000
Although 0 GHz is more preferable, all the samples in the present invention have Q × f> 20,000 GHz.

[0029]

As described above, according to the present invention,
A dielectric ceramic composition having a temperature coefficient τ _f of the resonance frequency close to zero, a large Q × f value, and a relatively large dielectric constant ε _r can be obtained.

[Brief description of the drawings]

FIG. 1 is a triangular diagram showing a composition range of a dielectric ceramic composition of the present invention, and a hatched portion including a boundary surrounded by ABCDEF is the range of the present invention.

FIG. 2 is a triangular diagram showing a composition range of a dielectric ceramic composition according to an embodiment of the present invention.

[Explanation of symbols]

1,3,5,6,7,8,10,12,14 Samples of the present invention corresponding to the sample numbers in Table 1 2,4,9,11,13,15 Comparative samples corresponding to the sample numbers in Table 1

Claims (1)

[Claims] 1. A general formula _{a · CaO-b · La 2} O 3 -c
TiO ₂ (however, the unit of a, b, and c is shown by mol%, and 10.0 ≦ a ≦ 25.0, 18.0 ≦ b ≦ 34.
0,50.6 ≦ c ≦ 70.0, a + b + c = 100 mol%), and ABCD in FIG.
A dielectric porcelain composition characterized by being in a hatched area surrounded by EF.