JPH0793234B2 - Ceramic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high frequency, a wide temperature range,
The present invention relates to a ceramic capacitor having an excellent Q value.

Conventional technology As a conventional ceramic capacitor, titanium oxide, barium titanate, strontium titanate, calcium titanate, magnesium titanate, barium zinc tantalate and barium zinc niobate compounds, and their compound sintered bodies, Ag It is known that electrode materials such as Pt, Pt, and Pd are applied in a paste form and baked.

These ceramic capacitors have a large dielectric constant and a small dielectric loss (tan δ), and have excellent properties as a capacitor.

Problems to be Solved by the Invention However, these ceramic capacitors also have a problem in their performance at high frequencies of 10 GHz or higher. The most problematic characteristic is an increase in loss at high frequencies, that is, a decrease in resonance Q value. The Q value at a high frequency involves both the dielectric and the electrode, and the optimization of the combination is the most important.

In recent years, as a high frequency transistor, a high mobility transistor using a two-dimensional electron gas has been developed, and the characteristics of this transistor are more excellent as the temperature is lower. Therefore, in applications such as satellite communication in which high-frequency and weak radio waves are handled, some measures have been taken to keep the entire system at a low temperature. However, in the conventional ceramic capacitor, the Q value of the high frequency is not significantly improved by this.

The present invention has been made in view of the above points, and an object thereof is to provide a ceramic capacitor having an excellent Q value at a high frequency and in a wide temperature range.

Means for Solving the Problems In order to solve the above problems, the present invention provides a layered perovskite structure type oxide superconductor sintered body powder particles 40 to 83% by weight, a glass component 2 to 22% by weight, and a metal component 15 to A ceramic capacitor having an electrode composed of 38% by weight and using an oxide sintered body as a dielectric is provided.

Effect The present invention can obtain a ceramic capacitor having a large Q value at a high frequency in a wide temperature range due to the above structure.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

(Example 1) Yttrium oxide (Y ₂ O ₃ ), barium oxide (BaO) and copper oxide (CuO) were weighed so as to be included in a ratio of Y ₁ Ba ₂ Cu ₃ , and after mixing, air at 950 ° C. Bake for 5 hours. This is pulverized and mixed again, and then fired in air at 950 ° C. for 10 hours. This is pulverized again and fired in air at 830 ° C. for 1 hour to obtain sintered powder particles.

Next, 40 to 83% by weight of the above-mentioned sintered powder particles, 2 to 22% by weight of lead borosilicate glass powder, and 15 to 38% by weight of silver powder as a metal component are mixed with a solvent containing a thickener, and then three-staged. Knead with a roller to make a paste. The thickener and the solvent are not particularly limited as long as they scatter when the paste is baked. In this example, ethyl cellulose dissolved in terpineol was used. A range of between 5 and 45% by weight of solvent containing thickener is preferred, relative to 55 to 95% by weight of solids.

Next, titanium oxide, barium titanate, strontium titanate, calcium titanate, magnesium titanate, barium zinc tantalate and barium zinc niobate compound (Ba (Zn _1/3
Ta _2/3 ) O ₃ −Ba (Zn _1/3 Nb _2/3 ) O ₃ ), six kinds of disc-shaped sintered bodies with a diameter of 5 mm and a thickness of 2 mm were made by the screen printing method. Printing was performed to form a thick film of about 20 μm on both sides of each disk-shaped sintered body. Then 80
A baking process was performed in air at 0 ° C. for 10 minutes to obtain an electrode.

14 GHz of the ceramic capacitor obtained in this way
The Q value at was measured at 77K. For comparison,
The Q value of a ceramic capacitor using a conventional silver electrode was also measured for each material. As a result, in the case of using the conventional silver electrode (the same thickness as that of the embodiment), the loss in the electrode is overwhelmingly larger than the loss in the dielectric at 14 GHz, and for any dielectric material, The Q value was almost corresponding to the loss of the electrode, and all were 100 or less. On the other hand, in the present example, the electrode was in the superconducting state at 77K, and the loss related to the electrode was much smaller than the loss of the dielectric, and the Q value corresponding to only the loss of the dielectric was obtained. Titanium oxide, barium titanate, strontium titanate, calcium titanate
0 or more, magnesium titanate, barium zinc tantalate and barium zinc niobate compound (Ba (Zn _1/3 Ta _2/3 ) O
_{For 3-} Ba (Zn _1/3 Nb _2/3 ) O ₃ ), a Q value of 1000 or more was obtained.

The Q value at room temperature was comparable to that of the conventional one.
When the amount of silver was 15% by weight or less, the Q value at room temperature decreased. It is considered that this is because the resistance value of the electrode at room temperature becomes high. If it exceeds 38% by weight,
The Q value at 77K decreased. It is considered that this is because the superconducting characteristics are adversely affected. Therefore, the amount of silver is preferably in the range of 15 to 38% by weight. That is, within this range, it is possible to obtain a capacitor having the conventional characteristics at room temperature and having a Q value far superior to that of the conventional one at the superconducting critical temperature or lower.

The oxide of the electrode used in this example showed a layered perovskite structure when examined by X-ray analysis.

FIG. 1 shows an embodiment of the structure of the present invention.
In FIG. 1, reference numeral 1 is an oxide sintered body dielectric, and 2 is an electrode made of an oxide superconductor and silver.

FIG. 2 shows a perovskite structure which is a constituent element of the crystal structure of the electrode superconductor in this example. In the figure, 3 contains Cu, 4 contains O, 5 contains Y or Ba, and these constituent elements are stacked in layers with a certain period. In an actual superconductor, this structure is considered to be an oxygen-deficient structure in which oxygen is appropriately removed.

When the amount of the glass powder was less than 2% by weight, the binding force of the electrode was weak, and a practical product in terms of strength could not be obtained. Also
If it exceeds 22% by weight, it becomes difficult to obtain an electrode having a small loss over a wide temperature range below room temperature and the superconducting critical temperature. Therefore, the glass component is preferably in the range of 22 to 2% by weight. In this range, all the baked electrodes were in the superconducting state at 77K, and the same result was obtained with respect to the Q value as long as it was in the superconducting state.

As the glass component, in addition to lead borosilicate glass, lead zinc borosilicate glass, bismuth borosilicate glass, and barium borosilicate glass gave similar results to those of this example. That is, any glass may be used as long as it has a function of melting and adhering at the baking temperature and reacting with the electrode material at the baking temperature to impair the superconducting properties of the electrode.

Other than silver, platinum, palladium, and gold were used as the metal material, and the same results as in this example were obtained. That is, any metal material may be used as long as it does not react with the electrode material at the baking temperature to impair the superconducting properties of the electrode.

Example 2 Lanthanum oxide (La ₂ O ₃ ), barium oxide (BaO) and copper oxide (CuO) were weighed so as to contain La _1.84 and Ba _0.16 Cu ₁ , respectively, and after mixing, Example 1 was performed. In the same manner as described above, sintered powder particles were obtained.

Next, using this raw material powder as an electrode material, Example 1
A ceramic capacitor was formed through the same process as described above. The Q value of the obtained ceramic capacitor was measured at 30 K at room temperature, and the result was compared with that of a conventional silver electrode. As a result, the same result as in Example 1 was obtained. That is, even in this case,
The electrode is a superconductor below the critical temperature, and the electrode loss of this example is extremely low, and a good Q value was obtained.

The results produced by changing the ratio of the sintered powder particles to the glass component and the metal component were the same as in Example 1. Moreover, the result when changing the kind of glass and the kind of metal was also the same.

The oxide of the electrode has a layered perovskite structure as in Example 1.

(Example 3) Rare earth oxides (oxides of Yb, Er, Ho, and Dy), barium oxide (BaO) and copper oxide (CuO) were used, and the ratio of rare earth oxides and barium oxide was 0.3 to 1 copper oxide. Various weighings were performed to obtain 0.7, and after mixing, the sintered body powder particles were obtained in the same manner as in Example 1.

Next, using this raw material powder as an electrode material, Example 1
A ceramic capacitor was formed through the same process as described above. The Q value of the obtained ceramic capacitor was measured at 50K at room temperature, and the result was compared with that of a conventional silver electrode. As a result, the same result as in Example 1 was obtained. That is, even in this case,
The electrode is a superconductor below the critical temperature, and the electrode loss of this example is extremely low, and a good Q value was obtained.

The results produced by changing the ratio of the sintered powder particles to the glass component and the metal component were the same as in Example 1. Moreover, the result when changing the kind of glass and the kind of metal was also the same.

The oxide of the electrode has a layered perovskite structure as in Example 1.

As described above, according to the method of the present invention, it is possible to obtain a ceramic capacitor having a large high frequency Q value in a wide temperature range.

FIG. 2 shows the crystal structure of the superconductor for an electrode of Example 1, but the layered perovskite structures of Examples 2 to 3 respectively have Y and Ba instead of Y and Ba in this structure. In this example, elements other than Cu and O used in the above example were replaced.

In the structure of this example, both the dielectric and the superconductor electrode are oxides, and the metal material is a noble metal. Therefore, the electrodes can be baked in an atmosphere containing oxygen, for example, in the air, and the electrodes can be produced without impairing the superconducting properties of the electrodes and the dielectric properties of the dielectric.

Also, since the dielectric is an oxide sintered body and the electrode is mainly composed of an oxide sintered body, the familiarity between the dielectric sintered body and the electrode during electrode baking is extremely good, and the electrode during baking is very good. No problems such as lowering of the superconducting critical temperature of the electrode due to peeling or cracking were observed. Therefore, according to the manufacturing method of the present embodiment, any combination of the oxide sintered body dielectric and the layered perovskite structure type oxide superconductor can be applied. For example, similar results are obtained when a compound of barium titanate and strontium titanate or a compound of strontium titanate and calcium titanate is used as a dielectric.

Further, in this example, a specific value was used as the thickness of the dielectric and the thickness of the oxide superconductor for an electrode, but the thickness of the dielectric is arbitrary, and the thickness of the electrode is the viscosity of the paste,
A thickness of several μm to 1000 μm can be arbitrarily obtained by changing the roughness of the screen used for printing.

In addition, in any of the examples, as a result of X-ray analysis of the crystal structure of the oxide sintered body powder in any of the examples, it already has a layered perovskite structure in the powder state, and from the measurement of the magnetic susceptibility, Diamagnetism was observed and it was found that the powder particles were already in the superconductor state. Therefore, the baking temperature is low and the baking time is short, whereby an oxide superconductor electrode can be obtained without the glass component adversely affecting the superconductor component.

The ceramic capacitor of the present invention has an extremely excellent Q value in a high frequency range over a wide temperature range, and when used in combination with a high frequency transistor using a two-dimensional electron gas, a high mobility transistor, etc. A high-performance amplifier, oscillator, etc. can be configured.

Effects of the Invention As described above, the present invention is an electrode composed of layered perovskite structure type oxide superconductor sintered powder particles 40 to 83% by weight, glass component 2 to 22% by weight, and metal component 15 to 38% by weight. And a ceramic capacitor using an oxide sintered body as a dielectric.

[Brief description of drawings]

FIG. 1 is a structural view showing one embodiment of the structure of the present invention, and FIG. 2 is a structure showing a perovskite structure which is a constituent element of the layered perovskite structure which is the crystal structure of the oxide superconductor used in the present invention. It is a figure. 1 ... Oxide sintered body dielectric, 2 ... Electrode containing oxide superconductor, 3 ... Cu, 4 ... O, 5 ... Y or Ba.

Claims (5)

[Claims] 1. A dielectric having a layered perovskite structure type oxide superconductor sintered body powder particles 40 to 83% by weight, a glass component 2 to 22% by weight, and a metal component 15 to 38% by weight. A ceramic capacitor characterized in that an oxide sintered body is used as. 2. A layered perovskite structure type oxide superconductor sintered body powder particles, wherein A-Ba-Cu oxide (where A is
Y, rare earth) is used, The ceramic capacitor according to claim (1). 3. The ceramic capacitor according to claim 2, wherein La, Yb, Er, Ho and Dy are used as the rare earth element. 4. A ceramic capacitor according to claim 1, wherein lead borosilicate glass, lead borosilicate zinc glass, bismuth borosilicate glass, and barium borosilicate glass are used as the glass component. . 5. A titanium oxide as the oxide sintered body dielectric,
The barium titanate, strontium titanate, calcium titanate, magnesium titanate, barium zinc tantalate and barium zinc niobate compounds, and the compounds thereof are used. Ceramic capacitor.