JPH07201224A - Dielectric ceramic composition and laminated dielectric component - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a dielectric porcelain composition having a high relative dielectric constant and a no-load Q value, a small temperature coefficient of resonance frequency, and capable of being fired at a low temperature in a microwave region. With the goal. [Structure] A dielectric ceramic composition is obtained which contains bismuth oxide, calcium oxide and niobium oxide as main components and is fired in an oxygen atmosphere.

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 used in a high frequency region such as a microwave and a millimeter wave and a laminated dielectric component.

[0002]

2. Description of the Related Art In recent years, along with the increase in communication using electromagnetic waves in the microwave region such as car phones, mobile phones, satellite broadcasting, etc., miniaturization of dielectric parts such as filter elements and resonators that compose the equipment Is required. In order to miniaturize such a dielectric component, the relative permittivity is high and the loss is low in the microwave region, that is, the no-load Q value is high, and the temperature change of the resonance frequency is small, that is, the dielectric It is important that the temperature change of the rate is small.

On the other hand, attempts have been made to miniaturize and enhance the functions of parts such as a resonator by forming a laminated structure of a conductor and a dielectric ceramic composition. However, when used in a high frequency region such as microwave, a conductor having high conductivity is required, and Cu, Au, Ag or their alloys must be used. Moreover, in the case of forming a laminated structure, it is necessary to simultaneously fire the dielectric material and the metal of the conductor. Therefore, the conductor metal does not melt and is not oxidized, that is, it is densely fired at a low temperature of 1050 ° C. or lower. A dielectric porcelain composition to be bound is required.

As a material having a high unloaded Q value, BaO--
The TiO ₂ —Sm ₂ O ₃ system is disclosed in JP-A-57-15309. This dielectric material has a relative permittivity of about 80, a high no-load Q value of about 2000 to 3000 at 2 to 4 GHz, and a temperature coefficient of a resonance frequency of about -400 to 400 ppm / ° C. However, the firing temperature is 130
Since it is as high as 0 ° C, it cannot be co-fired with a high conductivity electrode,
It could not be used for a dielectric component having a laminated structure.
A material that can be fired at a low temperature is Bi ₂ O ₃ —ZnO.
-Nb ₂ O ₅ system is disclosed in Japanese Patent Laid-Open No. 4-285046. This dielectric material is sintered at 850 to 1000 ° C., has a relative permittivity of 80 or more, an unloaded Q value of 100 or more at 2 to 4 GHz, and a temperature coefficient of resonance frequency of −150 ppm / ° C. or more. . However, the unloaded Q value was low and it was not practical as a dielectric material used in the microwave region.

As a dielectric material for solving the above problems, BiO _3/2 -CaO-NbO _5/2 system is disclosed in Japanese Unexamined Patent Publication No. Hei.
It is disclosed in Japanese Patent No. 225826. This dielectric material is provided as a dielectric porcelain composition which has both a high relative permittivity and a no-load Q value, a small temperature coefficient of resonance frequency, and is capable of low temperature sintering.

[0006]

However, this conventional dielectric material has a problem that the sintering density is not sufficiently high when fired in air or nitrogen, and there is a large variation in characteristics such as unloaded Q value. there were.

The present invention solves such a problem by providing a dielectric ceramic composition which has both a high relative permittivity and a no-load Q value, a small temperature coefficient of resonance frequency, and is densely sintered at low temperature. It is intended to be provided.

[0008]

To achieve this object, the dielectric ceramic composition of the present invention comprises bismuth oxide, calcium oxide and niobium oxide as main components and is fired in an oxygen atmosphere.

[0009]

With such a structure, the relative permittivity and the unloaded Q
Both values are high, the temperature coefficient of the resonance frequency is small, the characteristic variation is small, and moreover, the dielectric ceramic composition which is densely sintered at low temperature can be stably obtained. Furthermore, by using this dielectric ceramic composition, a small-sized and high-performance laminated dielectric component can be provided.

[0010]

【Example】

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described in detail.

High-purity Bi ₂ O ₃ and CaC as starting materials
O ₃ and Nb ₂ O ₅ were used and weighed so as to have the composition shown in (Table 1). These powders were placed in a polyethylene ball mill, and stabilized zirconia boulders and pure water were added and wet mixed for 5 to 20 hours. The obtained mixed powder was put into an alumina container and calcined at 700 to 850 ° C. for 1 to 3 hours. The calcined powder was placed in the ball mill, and boulders made of stabilized zirconia and pure water were added, and the mixture was wet ground for 5 to 20 hours to obtain a raw material powder.

To this raw material powder, 5 to 10 wt% of a 5% aqueous solution of polyvinyl alcohol was added as a binder, the mixture was granulated, rectified through a 30-mesh sieve, and then 100
It was molded into a columnar shape having a diameter of 13 mm and a thickness of 5 to 7 mm at MPa. The obtained molded body is put in a container made of magnesia, and 60
After incinerating the binder by heating at 0 to 650 ° C for 1 to 3 hours, the binder is burned in an oxygen stream of 1000 to 4000 cm ³ / min for 8 hours.
It sintered at 50-1050 degreeC for 1-4 hours, and obtained the sintered compact.
At the same time, as a comparative example, firing was performed in air and in a nitrogen atmosphere.

The density of the obtained sintered body was measured by the Archimedes method. Then, both surfaces of the obtained sintered body, which was fired at a temperature at which the density became maximum, were polished, and the dielectric property by microwave was measured. The measurement was performed by a dielectric resonance method, and a relative permittivity (hereinafter referred to as ε _r ), a no-load Q value (hereinafter referred to as Q value), and a temperature coefficient of resonance frequency (hereinafter referred to as γ _f ) were calculated. In the measurement of ε _r and Q value, the resonance frequency was 3 to 5 GHz. γ _f is -2
It measured in the range of 5-85 degreeC. Ten measurement samples were prepared and the characteristics were evaluated. The results are shown in (Table 1).

[0014]

[Table 1]

In Table 1, those marked with * are comparative examples outside the claims of the present invention.

As is clear from this (Table 1), according to this example, the sintered density was 6.95 g / cm ³ or more, the Q value was 400 or more, and the variation thereof was 5% or less. A sintered body is obtained.

As described above, the sintering density becomes higher when firing in an oxygen atmosphere than when firing in normal air.
The unloaded Q value also becomes higher. It is considered that this is because by supplying sufficient oxygen during firing, oxygen defects are reduced and a denser sintered body can be obtained. Moreover, it is considered that the denser sintered body reduces the dielectric loss and increases the unloaded Q value. In addition, it is considered that the reduction of large defects leads to a more homogeneous sintered body and the variation in characteristics.

Even in firing in an oxygen atmosphere, the firing temperature could be further lowered by adding Cu.

As is clear from the above, according to the dielectric ceramic composition of the present embodiment, by firing in an oxygen atmosphere, the dielectric ceramic composition is dense and has a high relative permittivity and a high no-load Q value. The dielectric ceramic composition having a small frequency temperature coefficient can be stably fired at a low temperature.

(Second Embodiment) A second embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a front sectional view of a laminated dielectric resonator of this embodiment, FIG. 2 is a side sectional view of a laminated dielectric resonator of this embodiment, and FIG. 3 is a laminated dielectric of this embodiment. It is a perspective view of a resonator. In the figure, 1 is a dielectric layer, 2, 3, 4 are internal conductor layers, and 5 is an external electrode.

High purity Bi ₂ O ₃ and CaC as starting materials
O ₃ , Nb ₂ O ₅ and CuO were used and weighed so as to have the composition shown in Sample No. 12 in (Table 1). The raw material powder was produced in the same manner as in Example 1. An organic binder, a solvent and a plasticizer were added to and mixed with the obtained raw material powder, and a dielectric sheet was formed by a doctor blade method. As the conductor electrode, the metal shown in (Table 2) was selected and kneaded with the vehicle to form a paste.

[0023]

[Table 2]

FIG. 4 is an exploded view of the laminated dielectric component in this embodiment. First, the internal conductor layer 2 was screen-printed on the dielectric layer 1 composed of a plurality of molded dielectric sheets. The dielectric layer 1 was provided thereon, and the inner conductor layer 3 was screen-printed thereon. The length of the inner conductor layer 3 to be the strip line was 13 mm. Further, the dielectric layer 1 was provided thereon, and the inner conductor layer 4 was screen-printed. Finally, the dielectric layer 1 was provided, pressure-bonded by a hot press, and heat-treated in air to incinerate the binder. After that, 1000-40
Each was fired at 900 ° C. in an oxygen stream of 00 cm ³ / min. At the same time, as a comparative example, firing was performed in air.
Finally, an Ag electrode as the external electrode 5 was baked in air to obtain a laminated dielectric resonator. The length of the inner conductor layer 3 which becomes the strip line after firing is 11.4 to 11.5 mm.
Met. Ten measurement samples were prepared and the characteristics were evaluated. The results are shown in (Table 2).

In Table 2, those marked with * are comparative examples outside the claims of the present invention.

As is clear from this (Table 2), according to this embodiment, the resonance frequencies are all around 850 MHz and Q
An excellent laminated dielectric resonator having a high value of 200 or more and a small variation can be obtained. Since the relative dielectric constant of the conventional low temperature fired substrate material is about 8, it is 31.5 mm in order to obtain the same resonance frequency with the same structure as the resonator of this embodiment.
Stripline length is required. However, since the relative dielectric constant of the dielectric ceramic composition of the present invention is as high as about 60, the strip line length can be shortened to 11.5 mm.
As a 0 MHz dielectric resonator, a very small size and excellent characteristics can be stably obtained.

It is also possible to obtain a smaller resonator by forming the strip line into a curved shape or a laminated shape. It is also possible to configure a bandpass filter or the like by combining these with a capacitor.

[0028]

As described above, according to the present embodiment, the dielectric ceramic composition containing bismuth oxide, calcium oxide and niobium oxide as the main components is fired in an oxygen atmosphere to obtain a relative dielectric constant. Both unloaded Q value is high,
The temperature coefficient of the resonance frequency is small, and moreover, the dielectric ceramic composition that is densely sintered at low temperature can be stably obtained.

Further, by using this dielectric ceramic composition, it is possible to stably provide a small-sized and high-performance laminated dielectric component that can be used in a high frequency region using a conductor having high conductivity. In particular, since it is possible to configure a small resonator system, it largely contributes to downsizing of communication devices such as car phones and mobile phones that use electromagnetic waves in the microwave range.

[Brief description of drawings]

FIG. 1 is a front sectional view of a laminated dielectric resonator according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a laminated dielectric resonator according to an embodiment of the present invention.

FIG. 3 is a perspective view of a laminated dielectric resonator according to an embodiment of the present invention.

FIG. 4 is an exploded view of a laminated dielectric resonator according to an embodiment of the present invention.

[Explanation of symbols]

 1 Dielectric Layer 2 Inner Conductor Layer 3 Inner Conductor Layer 4 Inner Conductor Layer 5 External Electrode

Claims (2)

[Claims] 1. A dielectric ceramic composition comprising bismuth oxide, calcium oxide and niobium oxide as main components and fired in an oxygen atmosphere. 2. A laminate in which a plurality of sheet-shaped dielectrics, which are dielectric compositions containing bismuth oxide, calcium oxide and niobium oxide as main components, and a plurality of internal conductors are alternately stacked and fired in an oxygen atmosphere. A laminated dielectric component including an input / output electrode provided in this laminated body.