JPS5936365B2 - semiconductor porcelain materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention was made in response to the requirements for electronic circuit design of a small ceramic capacitor with a small dielectric loss tangent and a small capacitance change due to DC bias or AC signal voltage. The present invention relates to a semiconductor ceramic material that has a high dielectric loss tangent, a small dielectric loss tangent, and excellent temperature characteristics and voltage dependence of capacitance.

BACKGROUND ART Among the semiconductor dielectric ceramics that have been produced in the past are those whose main component is barium titanate or barium titanate solid solution.

However, this type of capacitor cannot avoid the ferroelectric properties of barium titanate, so it has some fundamental drawbacks when applied to electrical circuit elements as a magnetic capacitor. That is, in the operating temperature range, the dielectric loss is influenced by the transformation point of the main component, and the dielectric loss becomes large due to the influence of the subcomponents added for the purpose of improving the capacitance-temperature characteristics. for example,
As shown in Table 1, conventional semiconductor capacitors have a frequency of 1
The dielectric loss tangent at kH2 and temperature of 20°C was 3.5%, and it was difficult to keep the capacitance temperature characteristics within ±15% in the temperature range of -25 to +85°C.

In addition, the capacitance change due to DC bias voltage is large, and 25
The capacitance when V bias is applied is approximately 30% lower than the capacitance when OV bias is applied. Furthermore, the capacitance value changes depending on the signal voltage input to the capacitor, and the frequency 1k
In H2, the capacitance value in the case of 4Vrms increases by about 5% compared to the capacitance value due to the signal voltage of 1Vrms.
The present invention is a semiconductor ceramic material containing strontium titanate as a main component, which eliminates the drawbacks of the above-mentioned barium titanate-based ceramic dielectric material, and has a large apparent dielectric constant characteristic of semiconductor ceramic capacitors. It provides:

In order to briefly demonstrate the effects of the present invention, a comparison with the conventional example will be made first.
Shown in the table.

In Table 1, the DC bias column of the capacitance change rate shows the capacitance change rate when the bias voltage is 0 V when 25 V DC is applied as the bias voltage, and the AC signal voltage column shows the capacitance change rate when the bias voltage is 0 V when 4 V rms is applied. The temperature column shows the capacitance change rate with respect to the capacitance at 20°C in the temperature range of -25 to +85°C, and the insulation resistance shows the resistance value after 1 minute after applying a DC voltage of 50 V. Ta.

In addition, the relative dielectric constant and specific area capacitance are at a frequency of 1 kHz and a voltage of 1 V.
It is calculated from the capacitance value measured at 20°C with a sine wave of rms, and the dielectric loss tangent is calculated from the equivalent resistance Rc measured at 20°C with a sine wave of frequency 1kHz and voltage 1Vrms.
It was calculated by δ=2πFRcCs (where Cs is the bridge reference capacitance value 1ItF). Furthermore, in order to compare the capacitance temperature characteristics and DC bias dependence in detail, the capacitance temperature characteristics are shown in FIG. 1, and the DC bias dependence of the capacitance is shown in FIG. As is clear from Table 1, Figures 1 and 2, the products of the present invention are superior to conventional products in terms of dielectric loss tangent, insulation resistance, capacitance temperature characteristics, DC bias voltage dependence, and signal voltage dependence. It is excellent. below,
The present invention will be explained in detail.

In the present invention, the composition described above is sintered and then subjected to a forced reduction treatment. A semiconductor magnetic capacitor using the semiconductor ceramic material according to the present invention can be manufactured, for example, by the following method.

That is, raw materials weighed in an accurate proportion to a predetermined composition ratio are mixed in a ball mill or the like, pre-calcined in air at 1100 to 1150°C, and then ground in a ball mill to obtain a prepared powder. In addition to oxides, the raw materials used at this time may of course be compounds that become oxides when heated, such as carbonates and oxalates. An organic binder such as polyvinyl alcohol is added to the prepared powder thus obtained, and pressure molding is performed at a pressure of 500 to 1400 kg/C7Il, followed by firing at 1250 to 1350°C.

Note that the atmosphere during firing is air, and the holding time at the maximum temperature may generally be about 1 to 6 hours. The fired porcelain is subjected to forced reduction treatment in hydrogen using a hydrogen furnace to convert it into a semiconductor. The appropriate treatment temperature at this time is 1200 to 1350°C. The surface of the semiconductor porcelain thus obtained is coated with 5 to 20 m9 of Bi2O3 powder, and heat treated in air at 1250 to 1350°C to diffuse Bi2O3 into the porcelain and insulate the grain boundaries. A semiconductor ceramic capacitor has been obtained which has excellent dielectric loss tangent, capacitance temperature characteristics, and capacitance bias voltage dependence, and has a high dielectric constant compared to the conventional capacitor.

Next, examples of the present invention will be described.

However, SrO, Tl
Powders of O2, Ne2O3, and ZnO were each accurately weighed, and a mixture thereof was wet-mixed.

However, SrcO3 having the same molar ratio as SrO was used. These mixtures were preliminarily calcined in air at 1140° C. for 2 hours, and then ground in a ball mill to obtain a prepared raw material powder. Afterwards, add 3.0% polyvinyl alcohol to the adjusted powder.
% by weight, pressure-molded into a disk with a diameter of 16 mm and a thickness of 0.7 mm at a pressure of 1200 kg / A disk-shaped semiconductor porcelain with a diameter of about 14 mmφ and a thickness of about 0.6 mm was obtained by reduction in hydrogen at 1300° C. for 2 hours. 5 to 20Tnf7 of Bl2O3 powder was applied to the surface of the semiconductor porcelain thus obtained.
Bl2
By diffusing O3 inside the porcelain, the grain boundaries are insulated,
A silver paste was applied to the disc-shaped dielectric ceramic obtained by a conventional method, dried, and fired at 800° C. for 30 minutes to form a silver electrode.

Table 2 shows the results of measuring the electrical characteristics of each sample of the capacitor thus produced.

In addition, the capacitance and dielectric loss tangent are determined using a capacitance bridge at a frequency of 1 kHz and an input voltage of 1 Vr at 20°C.
ms, and the insulation resistance is measured at DC 50 ms using an insulation resistance meter.
The value was measured after applying V for 1 minute. Also, the relative dielectric constant (εr) is 14.
It was calculated using the IU formula.

The dielectric loss tangent is extremely small, and the insulation resistance is several times to several tens of times higher.

Note that sample numbers 2 to 8, 11 to 18, and 20 are related to the present invention, and sample numbers 1, 9, 10, and 19 are outside the scope of the present invention, and have small dielectric constants and dielectric loss tangents. and extremely low insulation resistance.

Therefore, from the above results, the semiconductor ceramic material of the present invention has x
If it is less than 84.60 mol%, the insulation resistance will be lower than 109Ω, making it unsuitable as a dielectric material, and 97.54 mol%.
If it exceeds this value, the insulation resistance will show a high value, but the dielectric constant will decrease and the dielectric loss tangent will increase, which is not suitable for the purpose.

Where y is less than 0.26 mol% or more than 1.47 mol%, the dielectric constant is too small. z is 2.2
If it is less than mol%, the dielectric constant is extremely low and the dielectric loss tangent is high. Furthermore, if z exceeds 14.10 mol%, the insulation resistance will be extremely poor and the porcelain will fuse during firing, which is unfavorable in terms of manufacturing. As explained above, the semiconductor ceramic material according to the present invention has a lower dielectric loss tangent, better capacitance-temperature characteristics, smaller capacitance change due to DC bias voltage or signal voltage, and higher dielectric constant than conventional products. It has characteristics that could not be obtained with the materials proposed by the authors, and is of high industrial value.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a comparison diagram of capacitance change rate-temperature characteristics of the present invention and a conventional example, and FIG. 2 is a comparison diagram of capacitance change rate-DC bias voltage characteristics of the present invention and a conventional example.

Claims (1)

[Claims] 1 XSrTiO_3+y/2Me_2O_3・2Ti
O_2 + zZnO (Me = Y, Dy or La) where x + y + z = 100, consisting of x = 84.60 to 97.54 mol% y = 0.26 to 1.47 mol% z = 2.20 to 14.10 mol% A semiconductor ceramic material characterized by sintering a composition and subjecting it to forced reduction.