JPH08277161A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE: To obtain a dielectric ceramic composition by adding a subsidiary component to a specific main component, having a high dielectric constant, low temperature dependence of dielectric constant and a low melting point, capable of using an inner electrode material and being sintered at a low temperature. CONSTITUTION: High-purity barium carbonate, neodymium oxide, samarium oxide, titanium oxide, lead oxide and bismuth oxide as main raw materials and silicon dioxide, zinc oxide and boric acid anhydride as subsidiary raw materials are weighed in given ratios, respectively, blended in a wet state, dried, calcined, incorporated with a binder, molded, baked at 1,000-1,350 deg.C for about 2 hours to give the objective dielectric ceramic composition comprising main components of a composition formula xBaO.yNd2 O3 .zSm2 O3 .uTiO2 .vPbO.wBi2 O3 (0.080<x<0.160, 0.121<y<0.130, 0.005<z<0.030, 0.650<u<0.700, 0.045<v<0.100, 0.005<w<0.045, x+y+z+u+v+w=1) and subsidiary components composed of 1.2-4.0wt.% of SiO2 , 0.2-3.5wt.% of ZnO and 0.1-2.5wt.% of B2 O3 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency dielectric ceramic composition which constitutes a resonator or the like used mainly in a region called a microwave band.

[0002]

2. Description of the Related Art In recent years, high frequency dielectric porcelain has been used in antenna duplexers and voltage controlled oscillators (VCOs) of radio communication equipment such as car phones, mobile phones and cordless phones.
It is often used as a material for resonators used in, for example, filters used in CATV tuners. By using a material with a high dielectric constant for these materials, the high frequency wavelength can be changed to ε _r ^-1/2 (ε _r : relative dielectric constant) in vacuum.
The length can be shortened to 1 wavelength, 1/2 wavelength, or 1/4 wavelength (length thereof), which is a resonance condition of high frequency. Therefore, if this material is used, it is easy to miniaturize an electronic (functional) component that processes an electric signal by utilizing high frequency resonance (phenomenon).

The characteristics required for the high-frequency dielectric ceramics are as follows: (1) The high-frequency wavelength is ε _r ^{-1/2 in the} dielectric.
The relative permittivity (ε
_The larger _r ), the smaller the size. Therefore, the relative permittivity (ε _r ) is as large as possible, (2) the dielectric loss (1 / Q) in the high frequency band is small, that is, the Q value is large, and (3) the resonance frequency of the temperature change. There are three characteristics: a small rate of change, that is, a small temperature dependence of the relative dielectric constant (ε _r ).

In the microwave band, when it is applied in a region of about 1 GHz, which is a relatively low frequency band used for car telephones, personal radios, cordless telephones, etc., the wavelength becomes considerably long, so that the size of a resonator or the like is small. In order to achieve high dielectric constant, the dielectric ceramic composition must have a relative permittivity (ε
_r ) needs something quite high.

Conventionally, as this type of dielectric porcelain composition, for example, BaO--Nd ₂ O ₃ --TiO ₂ --Bi ₂ O ₃ system composition, BaO--Nd ₂ O
₃ -TiO ₂ -PbO-based compositions and the like are known.

[0006]

However, even in these materials, the relative permittivity (ε _r ) is about 70 to 90, and if an attempt is made to obtain a dielectric constant (ε _r ) higher than that, The temperature characteristic deteriorates, such as the Q value suddenly deteriorating.
There has been a limit to increase the relative permittivity (ε _r ) and reduce the size of the resonator and the like.

In addition, the internal electrode paste is printed on the dielectric green sheet to stack them, and then the internal electrode paste and the dielectric green sheet are simultaneously sintered,
By designing so-called laminated dielectric resonators and filters in which external electrodes are formed on this sintered body, the internal conductor shape is designed in various shapes, and the size of the sintered body is compared with the resonance wavelength. It is also considered to be significantly smaller.

However, since electrodes used in the microwave band are required to have low resistance, metals such as Au, Ag, Cu and Al are generally used as electrodes in resonators and the like in this band. However, a composition that sinters at a temperature lower than the melting points of those metals is required for simultaneous sintering.

However, the conventional high-frequency dielectric ceramics are sintered at 1300 to 1500 ° C., and metal materials such as Au, Ag, and Cu suitable for the microwave band cannot be adopted as the internal electrode material. There was a problem such as.

The present invention has been made in view of the above problems, and has a high relative permittivity (ε _r ), a low dielectric loss, and a low relative permittivity, which can further reduce the size of a high frequency resonator or the like. The temperature dependence of (ε _r ) is small and stable, so the resonance frequency of the manufactured dielectric resonator is low, and low melting point Au, Ag-Pd, etc. can be used as internal electrode materials. An object of the present invention is to provide a dielectric ceramic composition that can be sintered by.

[0011]

[Means for Solving the Problem and Its Effect] As a result of repeated studies to achieve the above-mentioned object, the present inventor has found that BaO, Nd ₂ O _3, Sm
_{2 O 3, TiO 2, PbO} , SiO 2, ZnO in a system consisting of Bi ₂ O _3, by the addition of B ₂ O _3, shows a large specific dielectric constant (epsilon _r), relative dielectric constant (epsilon _r ), The temperature dependence of the resonance frequency in the resonator is small, and has a high Q value,
Moreover, it is possible to use Au and Ag-Pd as internal electrodes.
The inventors have found that a dielectric ceramic composition that can be sintered at a low temperature of 50 ° C. can be obtained, and completed the present invention.

Namely, the dielectric ceramic composition according to the present invention, the composition formula _{xBaO · yNd 2 O 3 · zSm} 2 O 3 · uTiO 2 · vPbO · wBi 2 O 3 However, 0.080 <x <0.160 0.121 < y <0.130 0.005 <z <0.030 0.650 <u <0.700 0.045 <v <0.100 0.005 <w <0.045 x + y + z + u + v + w = 1 1.2 to 4.0% by weight of SiO ₂ as a minor component ZnO 0.2 to 3.5% by weight % And B ₂ O ₃ are added in a proportion of 0.1 to 2.5% by weight.

According to the dielectric ceramic composition having the above structure, the relative permittivity (ε _r ) and the Q value are high, the temperature dependence of the resonance frequency is small, and Au and Ag-Pd are used as the internal electrodes. It is possible to obtain a dielectric ceramic composition that can be sintered at a low temperature.

Therefore, the size of the high-frequency resonator, the filter, etc. can be greatly reduced, and the usefulness thereof is extremely large.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric ceramic composition according to the present invention is based on REO (rare earth oxide) -BaO-TiO ₂ as a main component, and Nd ₂ O ₃ and Sm ₂ O as rare earth oxides. ₃ was used, to which PbO and Bi ₂ O ₃ were added. Then, in order to enable low temperature sintering at 1000 ° C. to 1050 ° C., SiO ₂ , ZnO, and B ₂ O ₃ are added as auxiliary components.

When each component deviates from the above range, 1000 ° C.
It becomes impossible to sinter at a temperature as low as ~ 1050 ℃, or even if it is possible, the relative dielectric constant (ε _r ) is low, or the temperature coefficient (τf) of the resonance frequency is within ± 20ppm / ℃. It comes out or the Q value becomes as low as 1500 or less.

[0017]

[Examples and Comparative Examples]

(I) Adjustment of dielectric ceramics High-purity barium carbonate (BaCO ₃ ), neodymium oxide (Nd)
₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), titanium oxide (TiO ₂ ),
Lead oxide (PbO), bismuth oxide (Bi ₂ O ₃ ), silicon dioxide (SiO ₂ ), zinc oxide (ZnO), and boric anhydride (B ₂ O ₃ ) are weighed in the ratios shown in Table 1 below. did.

The above starting materials were wet mixed for one day in a ball mill and then dried.

The above mixture was calcined at a temperature of about 900 ° C. for about 2 hours.

The calcined mixture was wet-ground for one day in a ball mill and then dried.

About 1% by weight of a binder was added to the above dry powder to adjust the particle size.

Molded at a pressure of about 1000 kg / cm ² , 1000 to 13
It was baked in air at 50 ° C. for about 2 hours.

(II) Measurement of characteristics The obtained dielectric porcelain was measured by a dielectric cylinder resonator method at a resonance frequency of 3.0 to 4.0 GHz, relative permittivity (ε _r ), Q value and temperature coefficient (τf) of resonance frequency. Was measured.

The composition of the dielectric ceramic composition, the sintering temperature, and the characteristics of the dielectric ceramic composition are shown in Tables 1 and 2 below.

[0025]

[Table 1]

[0026]

[Table 2]

Below, based on Tables 1 and 2, the problems of the comparative examples outside the composition range according to the present invention will be described by comparing the examples and the comparative examples.

When x> 0.160: As in No. 5, the sintering temperature is
1100 ° C. or higher is required and the object of the present invention cannot be achieved.

When x <0.080: The Q value becomes low as in No. 12.

When y> 0.130: As in No. 6, the sintering temperature is
1100 ° C or higher is required.

When y <0.121: As in No. 7, the sintering temperature is
1100 ℃ or more.

When z> 0.030: As in No. 9, τf becomes large on the negative side.

When z <0.005: As in No. 8, τf becomes large on the positive side.

When u> 0.700: As in No. 7, the sintering temperature is
1100 ℃ or more.

When u <0.650: The Q value becomes low as in No. 5.

When v> 0.100: The Q value becomes low like No.12.

When v <0.045: The Q value becomes low as in No. 13.

When w> 0.045: The Q value becomes low as in No. 13.

When w <0.005: As in No. 15, τf becomes large on the positive side.

When SiO ₂ > 4.0% by weight: ε _{r as in} No. 3
Is small.

When SiO ₂ <1.2% by weight: No. 2, No. 18, N
The sintering temperature is 1100 ℃ or higher as in o.21.

When ZnO> 3.5% by weight: Q as No. 24
The value becomes low.

When ZnO <0.2% by weight: As in No. 19, the sintering temperature becomes 1100 ° C or higher.

When B ₂ O ₃ > 2.5% by weight: Q as No. 26
The value becomes low.

When B ₂ O ₃ <0.1% by weight: The sintering temperature becomes 1100 ° C. or higher as shown in No. 16.

As described above, the above-mentioned problems remain in the comparative example.

On the other hand, sample No. 1 within the composition range according to the present invention. , 1, 4, 10, 11, 14, 17, 20, 22, 23, 25 have a high relative dielectric constant (ε _r ) of 65.3 to 78.2 and a Q value of f × Q = 1537 to It is as high as 2650, and the temperature coefficient (τf) of the resonance frequency is stable at −10.8 to +9.1 ppm / ° C. and can be sintered at 1000 to 1050 ° C., thus achieving the object of the present invention.

Claims (1)

[Claims] 1. The composition formula is xBaO.yNd ₂ O ₃ .zSm ₂ O ₃ .uTiO ₂ .vPbO.wBi ₂ O ₃ where 0.080 <x <0.160 0.121 <y <0.130 0.005 <z <0.030 0.650 <u < 0.700 0.045 <v <0.100 0.005 <w <0.045 x + y + z + u + v + w = 1 to the main component, SiO ₂ is 1.2 to 4.0 wt% ZnO is 0.2 to 3.5 wt% and B ₂ O ₃ is 0.1 to 2.5 wt% % Of the dielectric ceramic composition.