JPH0793233B2 - Ceramic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic capacitor having an excellent Q value at high frequencies.

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 thereof is the most important. In recent years, a high mobility transistor using a two-dimensional electron gas has been developed as a high frequency transistor. The lower the temperature, the better the characteristics of this transistor. Therefore, in applications such as sanitary communications where 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 high frequencies.

Means for Solving the Problems In order to solve the above problems, the present invention has an electrode composed of layered perovskite structure type oxide superconductor sintered body powder particles 40 to 98% by weight and a glass component 2 to 60% by weight. A ceramic capacitor using an oxide sintered body as a dielectric is provided.

Effects The present invention can obtain a ceramic capacitor having a large Q value at high frequencies 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 98% by weight of the sintered powder particles and 2 to 60% by weight of lead borosilicate glass powder are mixed with a solvent containing a thickener and kneaded with a three-stage roller to form 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. 55-95% by weight of solids
On the other hand, a range of 5 to 45% by weight of the solvent containing the thickener is preferable.

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 electrode 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 a layered perovskite structure type oxide superconductor electrode.

FIG. 2 shows a perovskite structure which is a constituent element of the crystal structure of the electrode superconductor of 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 a superconductor as an electrode. Therefore, the oxide superconductor powder particles and the glass component are preferably in the ranges of 40 to 98% by weight and 60 to 2% by weight, respectively. In this range, all the baked electrodes were in the superconducting state at the measurement temperature, and as long as they were in the superconducting state, the same result was obtained regarding the Q value.

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 reacts with the electrode material at the baking temperature to impair the superconducting characteristics 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 30K and compared with that of a conventional silver electrode. As a result, the same result as in Example 1 was obtained. That is, also in this case, the electrode was a superconductor, and the electrode loss was extremely low in this example, and a good Q value was obtained.

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

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 and compared with that of a conventional silver electrode. As a result, the same result as in Example 1 was obtained. That is, also in this case, the electrode was a superconductor, and the electrode loss was extremely low in this example, and a good Q value was obtained.

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

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.

FIG. 2 shows the crystal structure of Example 1. The layered perovskite structure of Examples 2 to 3 is used in each Example instead of Y and Ba. The elements are replaced by elements other than Cu and O.

In the structure of this embodiment, both the dielectric and the superconductor electrode are oxides. 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 each 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, the powdery state already had a layered perovskite structure, and the magnetic susceptibility was measured. , Diamagnetism was observed, and it was found that the powder particles were already in a 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 at high frequencies at low temperatures, and when used in combination with high-frequency transistors such as high-mobility transistors using a two-dimensional electron gas at low temperatures, the performance is extremely high. It is possible to configure an amplifier, an oscillator, etc. with good performance.

As described above, the present invention has an electrode composed of layered perovskite structure type oxide superconductor sintered powder particles 40 to 98% by weight and a glass component 2 to 60% by weight, and has an oxide as a dielectric. A ceramic capacitor using a sintered body is provided.

[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, 3 ... Cu, 4
…… O, 5 …… Y or Ba.

Claims (5)

[Claims] 1. A layered perovskite structure type oxide superconductor sintered body powder particles having 40 to 98% by weight and an electrode composed of 2 to 60% by weight of a glass component, and an oxide sintered body is used as a dielectric. A ceramic capacitor characterized in that. 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.