JPH06283024A - Dielectric porcelain composition - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a dielectric ceramic used in a microwave region, and an object thereof is to independently control the relative permittivity and the temperature coefficient of the resonance frequency. [Composition] A composition comprising lead oxide, calcium oxide, iron oxide, niobium oxide, tungsten oxide and titanium oxide is prepared by using a compound represented by the general formula (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ). _1-y Ti _y }
O _{3 + a} or (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ) _1-z (Fe
_2/3 W _1/3 ) _z } O _{3 + a} . Further, a dielectric ceramic composition is obtained by substituting a part of Pb and Ca with Sr and a part or all of Nb with Ta.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic used in the microwave region.

[0002]

2. Description of the Related Art In recent years, there has been a demand for downsizing of equipment with the progress of communication using electromagnetic waves in the microwave range, such as car telephones, portable telephones, and satellite broadcasting.
For this purpose, it is necessary to reduce the size of individual parts that make up the device. In these devices, the dielectric is incorporated as a dielectric resonator in a filter element or an oscillating element. When the same resonance mode is used, the size of the dielectric resonator is inversely proportional to the square root of the relative permittivity (ε _r ) of the dielectric material. Materials with a dielectric constant are needed. In addition, for practical use as a dielectric resonator, it is necessary that the loss be low in the microwave region, that is, the Q value be high, and that the temperature coefficient (τ _f ) of the resonance frequency be small.

Although many porcelains for dielectric resonators have been developed so far, a BaO-TiO ₂ -Sm ₂ O ₃ system is particularly known as a porcelain having a high dielectric constant.
No. 9 publication. This system has a relative dielectric constant of about 80, a high Q value of about 3000 at 2 to 4 GHz, and a temperature coefficient of a small resonance frequency. On the other hand, dielectric porcelain having a higher relative dielectric constant has also been reported. Above all, a (Pb _1-x Ca _x ) _{1 + a} (Fe _1/2 Nb _1/2 ) O _{3 + a-} based dielectric porcelain is disclosed in JP-A-5-20925. Practical Q even when it has a high relative permittivity above
It has value and temperature characteristics. Further, the sintering temperature is 115
Relatively low at around 0 ° C.

[0004]

[Problems to be Solved by the Invention] However, (Pb _1-x Ca _x )
_{In the case of 1 + a} (Fe _1/2 Nb _1/2 ) O _{3 + a-} based dielectric porcelain, when x is determined, the relative permittivity and the temperature coefficient of the resonance frequency are determined, and τ _f = 0 Since the relative permittivity at that time could not be changed, it was not practical. Figure 4 shows (Pb _1-x Ca _x ) _{1 + a} (Fe
_The change in relative permittivity with respect to the temperature coefficient of the resonance frequency when x of the _1/2 Nb _1/2 ) O _{3 + a} system is changed is shown. In the case of the above composition system, the relative permittivity when τ _f = 0 is 90, and this value cannot be lowered or raised. In order to put this composition system into practical use, a technique for independently controlling the relative permittivity and τ _f , that is, a technique for shifting the curve in FIG. 4 to the high permittivity side or the low permittivity side is required. In addition, it is desirable that the sintering temperature be lower in consideration of manufacturing cost and variations in characteristics.

The present invention controls the relative permittivity and τ _f of conventional materials independently, that is, raises or lowers the relative permittivity when τ _f = 0, and sinters. The purpose is to reduce the temperature.

[0006]

In order to achieve this object, the general formula is (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ) _1-y Ti _y }.
O _{3 + a} or (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ) _1-z (Fe
_2/3 W _1/3 ) _z } O _{3 + a} . Further, a dielectric ceramic composition is obtained by substituting a part of Pb and Ca with Sr and a part or all of Nb with Ta.

[0007]

In Fig. 1, Ti and (Fe
_2/3 W _1/3 ) substitution effect. It can be seen that Ti substitution has the effect of lowering the relative permittivity of τ _f = 0, and (Fe _2/3 W _1/3 ) substitution has the effect of increasing the relative permittivity of τ _f = 0. Therefore, according to the dielectric ceramic composition of the present invention, the relative permittivity and τ _f can be controlled independently. Further, Sr and Ta are effective in lowering the sintering temperature.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) Embodiment 1 corresponds to an embodiment of the present invention described in claim 2.

The starting material is Pb which is chemically highly pure.
O, CaCO ₃ , Fe ₂ O ₃ , Nb ₂ O ₅ , and TiO ₂ were used. After correcting the purity of the raw materials, the composition was adjusted to (Pb
_1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ) _1-y Ti _y } O _{3 + a} , where x, y, and a are the columns of the composition of (Table 1) It was weighed so as to have various values shown in. In FIG. 2, the claims of x and y are shown by diagonal lines (including the boundary portion). 1 to 29 in FIG. 2 correspond to the sample numbers in (Table 1).

These powders were placed in a polyethylene ball mill, stabilized zirconia boulders having a diameter of 5 mm and pure water were added and mixed for 17 hours. After mixing, the slurry is dried, put in an alumina crucible and heated at 800 to 950 ° C for 2 hours.
I calcined for an hour. The calcined body was crushed by a raikai machine, crushed by the above-mentioned ball mill for 17 hours, and dried to obtain a raw material powder. To this powder, 6% by weight of a 5% aqueous solution of polyvinyl alcohol was added as a binder, mixed, and then granulated through a 32 mesh sieve, and the diameter was 13 m at 100 MPa.
m, and a thickness of about 5 mm was pressed into a cylindrical shape. After the molded body is heated at 600 ° C. for 2 hours to incinerate the binder, it is put into a porcelain container made of magnesia together with a calcined powder of the same composition to prevent evaporation of PbO, and the lid is closed from 1000 to 12
Baking was performed by holding at various temperatures of 00 ° C. for 2 hours. The dielectric properties of the sintered body that was fired at the temperature at which the density was highest were measured by microwaves. The resonance frequency and the Q value were obtained by the dielectric resonator method. The dielectric constant was calculated from the dimensions of the sintered body and the resonance frequency. The resonance frequency was 2 to 5 GHz.
In addition, the resonance frequencies at -25 ° C, 20 ° C, and 85 ° C were measured, and the temperature coefficient (τ _f ) was calculated by the least square method. The results are shown in (Table 1).

[0012]

[Table 1]

As shown in Table 1, when y = 0, τ
The relative permittivity when _f = 0 was almost 90 (composition near sample number 3 #), whereas when y = 0.2, τ _f = 0.
At that time, the relative dielectric constant was about 75 (composition near sample number 25). Thus, it is understood that the introduction of Ti can reduce the relative permittivity of τ _f = 0. When y = 0, the Q value was 1510 (sample number 3 #) when the relative permittivity was 90, but when y = 0.1, the relative permittivity was 97, as shown in sample number 13. Despite the increase, the Q value increased to 1830. It can be seen that the introduction of Ti also has the effect of increasing the Q value. In the compositions included in the scope of the claims, the dielectric constant was 70 or more, the Q value was 500 or more, and the absolute value of the temperature coefficient of the resonance frequency was 100 ppm / ° C. or less.

For compositions outside the claims, the straight line BC of FIG.
When x becomes larger, the relative dielectric constant becomes lower than 70,
When y was larger than the straight line CD, the Q value was low when the relative permittivity was the same as when y = 0, and when x was smaller than the straight line AD, the temperature coefficient of the resonance frequency was +100 ppm / ° C. or higher. In addition, the value of a becomes smaller than 0, or 0.
When it became larger than 8, the Q value decreased sharply.
Therefore, it was judged to be not practical as a microwave dielectric and was excluded from the claims.

(Embodiment 2) Embodiment 2 claims 3 and 4.
It corresponds to an embodiment of the invention described.

The method for producing the sintered body and the evaluation of the properties are evaluated in the examples.
Since the method is the same as that described in 1, the description thereof will be omitted. Composition studied
Is {(Pb_0.43Ca_0.57)_1-zSr_z}_1.0{(Fe
_1/2(Nb _1-bTa_b)_1/2)_0.9Ti_0.1} O₃Is. S
The starting materials for the r and Ta components are SrCO₃And
And Ta₂O_FiveWere used respectively. The results are shown in (Table 2).
The sintering temperature in (Table 2) is the temperature at which the density becomes maximum.

[0017]

[Table 2]

From Table 2, it can be seen that the sintering temperature was lowered by introducing Sr within the claimed range. Also, the relative permittivity and Q value were slightly improved. The value of z is 0.4
When it became larger, the Q value decreased, and the temperature coefficient of the resonance frequency also increased positively.

Further, by substituting Ta for Nb,
The sintering temperature has decreased. It is believed that this will lead to a reduction in manufacturing cost and suppression of variations in characteristics.

(Embodiment 3) Embodiment 3 corresponds to an embodiment of the present invention described in claims 5, 6, and 7.

The method of manufacturing the sintered body and the evaluation of its characteristics are the same as the method described in Example 1, and therefore the description thereof is omitted. The composition studied was (Pb _1-xy Ca _x Sr _y ) _{1 + a} ((Fe _1/2 (Ta _1-m Nb _m ) Nb _1/2 ) _1-z (Fe
A _{2/3 W 1/3) z}} O 3 + a. Numbers 1 to 22 are Sr-free (y = 0) compositions and correspond to claims 5 and 7. Numbers 23 to 45 contain Sr and correspond to claims 6 and 7. Starting materials for the Sr, Ta, and W components include SrCO ₃ , Ta ₂ O ₅ , and WO ₃
Were used respectively. The results are shown in (Table 3) and (Table 4).
In FIG. 3, the claims of x and y are shaded (including the boundary).
Indicate. 23 to 45 in FIG. 3 correspond to the sample numbers in (Table 4).

[0022]

[Table 3]

[0023]

[Table 4]

From (Table 3) and (Table 4), by introducing (Fe _2/3 W _1/3 ), the relative permittivity of τ _f = 0 is increased to about 100 as in sample No. 6. I see that you can.
The composition within the scope of the claims has a relative dielectric constant of 50 or more,
The characteristic is that the Q value is 500 or more and the absolute value of the temperature coefficient of the resonance frequency is 100 ppm / ° C or less. When W of more than the claimed range was added, the Q value was remarkably decreased, so it was excluded from the claimed range. All the compositions in the claims were sintered at a low temperature of 1100 ° C or lower.

[0025]

As described above, according to the dielectric ceramic composition of the present invention, due to the introduction of Ti and (Fe _2/3 W _1/3 ), the relative permittivity and t It became possible to control _f independently. Further, the introduction of Sr or Ta can lower the sintering temperature and improve the mass productivity. Therefore, it can be used as a material for a small-sized coaxial dielectric resonator. Further, the dielectric ceramics of the present invention can be used not only in dielectric resonators but also in circuit boards for microwaves, porcelain multilayer capacitors, etc., and are of great industrial value.

Elements other than those in the claims, particularly Ba,
Cr, Mn, Co, Ni, Cu, Zn, Si, Al, M
The inclusion of oxides such as g, Bi, Ge and Sb may be within the range that does not adversely affect the dielectric properties.

[Brief description of drawings]

Figure 1: (Pb _1-x Ca _x ) _{1 + a} (Fe _1/2 Nb _1/2 ) O _{3 + a} (Fe _1/2 Nb
Diagram showing the change in the relationship between the temperature coefficient of the resonance frequency and the relative permittivity when ( _1/2 ) is replaced with Ti or (Fe _2/3 W _1/3 ).

FIG. 2 is a shaded portion of the claims of x and y in claims 2 and 3 (however, the boundary portion of the straight line AB is not included).
The figure shown in

FIG. 3 is a diagram showing the claims of x and y according to claim 6 by a hatched portion (but not including a boundary portion of the straight line AD).

FIG. 4 is a diagram showing a relationship between a temperature coefficient of a resonance frequency and a relative permittivity when _{x of a} (Pb _1−x Ca _x ) (Fe _1/2 Nb _1/2 ) O ₃ system is changed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiji Nishimoto, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Ichiro Kameyama, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. When the general formula is represented by A _{1 + a} BO _{3 + a} (a ≧ 0), A contains at least Pb and Ca, Ca is 20% or more of A, B is at least Fe and N
A dielectric ceramic composition containing b, and one or more elements selected from Ti and W. 2. A composition comprising lead oxide, calcium oxide, iron oxide, niobium oxide, and titanium oxide is represented by the composition formula: (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ). _1-y Ti _y }
When expressed as O _{3 + a} , x and y are the following rectangles A, B, C,
And in the area surrounded by D (excluding y = 0), A: (x, y) = (0.43,0.0) B: (x, y) = (0.63 , 0.0) C: (x, y) = (0.74, 0.25) D: (x, y) = (0.57, 0.25) and a is in the range of 0.0 ≦ a ≦ 0.08 2. A dielectric porcelain composition according to claim 1. 3. A composition comprising lead oxide, calcium oxide, iron oxide, niobium oxide, titanium oxide, and strontium oxide having the compositional formula: {(Pb _1-x Ca _x ) _1-z Sr _z } _{1 + a} {(Fe _1/2 N
b _1/2 ) _1-y Ti _y } O _{3 + a} , x and y are the following rectangles A, B, C,
And in the area surrounded by D (excluding y = 0), A: (x, y) = (0.43,0.0) B: (x, y) = (0.63 , 0.0) C: (x, y) = (0.74, 0.25) D: (x, y) = (0.57, 0.25) and a and z are 0.0 ≦ a ≦ A dielectric ceramic composition having a range of 0.08 0.0 <z ≦ 0.4. 4. The dielectric ceramic composition according to claim 2, wherein part or all of Nb is replaced with Ta. 5. A composition comprising lead oxide, calcium oxide, iron oxide, niobium oxide, and tungsten oxide having the composition formula: (Pb _1-x Ca _x ) _{1 + a} {(Fe _1/2 Nb _1/2 ) _1-z (Fe
_2/3 W _1/3 ) _z } O _{3 + a} , x, z, and a are in the range of 0.43 <x ≤ 0.63 0.0 <z ≤ 0.5 0.0 ≤ a ≤ 0.08. A dielectric ceramic composition. 6. A composition comprising lead oxide, calcium oxide, strontium oxide, iron oxide, niobium oxide, and tungsten oxide having a compositional formula of (Pb _1-xy Ca _x Sr _y ) _{1 + a} {(Fe _{1 / 2} Nb _1/2 ) _1-z (Fe _2/3 W _1/3 ) _z } O
When expressed as _{3 + a} , z and a are in the range of 0.0 <z ≤ 0.7 0.0 ≤ a ≤ 0.08, and x and y are the following rectangles A, B, C,
A dielectric ceramic composition, which is in a region surrounded by and D (however, y = 0 is not included). A: (x, y) = (0.43, 0.0) B: (x, y) = (0.3, 0.13) C: (x, y) = (0.3, 0.4) ) D: (x, y) = (0.7, 0.0) 7. The dielectric ceramic composition according to claim 5, wherein part or all of Nb is replaced with Ta.