JPH0380322B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention has a voltage dependence property suitable for making voltage dependent nonlinear resistors (hereinafter referred to as varistors) used for abnormal voltage absorption and noise removal in various electrical and electronic devices. The present invention relates to a non-linear resistor ceramic composition. Conventional configurations and their problems Traditionally, various electrical and electronic devices have been used to absorb abnormally high voltages (hereinafter referred to as surges), remove noise,
SiC varistors and ZnO-based varistors, which have voltage-dependent nonlinear resistance characteristics, were used to eliminate sparks. The voltage-current characteristics of such a varistor can be approximately expressed as follows. I=(V/C) Here, I is current, V is voltage, C is a constant specific to the varistor, and α is a voltage nonlinear index. The α of SiC varistors is about 2 to 7, and the α of some ZnO-based varistors is as high as 50. Although such varistors have excellent performance in absorbing relatively high voltages such as surges, their low dielectric constant and small specific capacitance prevent them from absorbing low voltages below the varistor voltage (e.g. noise, etc.). ), and the dielectric loss (tanδ) is 5~5.
A large 10%. On the other hand, in order to eliminate these noises, semiconductor porcelain capacitors with an apparent permittivity of about 5×10 ⁴ to 6×10 ⁴ and a tan δ of around 1% can be used by appropriately selecting the composition and firing conditions. ing. However, if a current exceeding a certain limit is applied to the element due to a surge or the like, this semiconductor ceramic capacitor may be destroyed or may no longer function as a capacitor. For the reasons mentioned above, in electrical and electronic equipment, varistors are usually used in combination with capacitors and other parts (e.g. coils) for purposes such as surge absorption and noise removal.For example, noise filters are It is structured like this. Figure 1 shows a general conventional noise filter circuit, and Figure 2 shows a conventional noise filter circuit configured by combining a varistor, a capacitor, and a coil, where 1 is a coil, 2 is a capacitor, and 3 is a I'm a barista. However, the configuration shown in FIG. 2 has the disadvantage that the number of parts inside the device increases and it is contrary to the trend toward miniaturization of devices. Purpose of the Invention The present invention eliminates the drawbacks of conventional surge absorption and noise removal as described above, and provides a composite function that has the functions of both a varistor and a capacitor and can perform surge absorption and noise removal with a single element. The object of the present invention is to provide a porcelain composition suitable for making a varistor having a porcelain composition. Structure of the Invention In order to achieve the above-mentioned objects, the present invention uses SrTiO ₃ , Dy ₂ O ₃ as a metal oxide for promoting semiconductor formation, and Mg, Zr, Sn, Sb, W, Bi, Ni. ,
The present invention proposes a voltage-dependent nonlinear resistor ceramic composition containing a predetermined amount of at least one element selected from the group consisting of Fe. DESCRIPTION OF EMBODIMENTS The present invention will be specifically described below with reference to Examples. Example 1 SrTiO ₃ , Dy ₂ O ₃ and ZrO ₂ were weighed to have the composition ratio shown in Table 1 below, mixed wet for 6 hours using a ball mill, etc., dried, and then mixed in air. Calculate at 1000-1250℃ for 1-5 hours. After that, it was wet-pulverized for 4 hours using a ball mill etc.
After drying, 8wt% of organic binder (e.g. polyvinyl alcohol) was added and granulated.
(mm)φ×1.0(mm)t shape with a press pressure of 1.0t/cm ² . This molded body is placed in a reducing atmosphere (e.g.
It was fired for 1 to 6 hours at 1300 to 1450°C under N ₂ :H ₂ =10:1). The specific resistance of the fired body thus obtained is
0.1~0.8Ω. cm, and the average particle size was 20-50 μm. Next, this fired body is heated at 1000 to 1300℃ in air.
The sintered body 4 shown in FIG. 3 was obtained by firing for 0.5 to 5 hours.
Further, both surfaces of the sintered body 4 were polished with an abrasive such as SiC, and electrodes 5 and 6 were formed using a conductive metal such as Ag. The diameter of the above electrodes 5 and 6 is 5.0
(mm) φ. The characteristics of the device thus obtained are also shown in Table 1.

【table】

[Table] *... Comparative example Here, the characteristics of the element as a varistor are evaluated using the voltage-current characteristic equation described above: I = (V/C) This can be done by α and C in a constant (α is a non-linear index). However, since accurate measurement of C is difficult, in the present invention, 1 mA
The value of the varistor voltage per unit thickness (hereinafter _referred to as _{V 1nA} /mm) when _a varistor current of The characteristics of the varistor are evaluated based on the value of the varistor voltage (V _1nA is the varistor voltage when 1mA of varistor current is applied). In addition, the characteristics as a capacitor are evaluated using the dielectric constant ε and dielectric loss angle tan δ at a measurement frequency of 1 kHz. The above data shows the firing temperature and time in a reducing atmosphere.
1400℃, 2 hours, firing temperature and time in air
This was done at 1200℃ for 3 hours. As shown in Table 1, the amount of Dy ₂ O ₃ added is 0.005.
When the amount exceeds mol%, _SrTiO3 becomes a solid solution in the lattice of the crystal mainly composed of SrTiO3 during firing, and the specific resistance of the sintered body is reduced to 1.0Ω by controlling the valence. Since it can be lowered to around 1.2 cm, it can be used as a varistor by re-firing in air. However, if Dy ₂ O ₃
If it exceeds 10.000 mol%, it will no longer form a solid solution.
The specific resistance of the sintered body increases, making it unsuitable for use as a varistor. ZrO ₂ segregates at the grain boundaries of crystals mainly composed of SrTiO ₃ during firing, increases the resistivity of the grain boundary layer, and contributes to increasing the nonlinearity of the sintered body. Such an effect appears when the amount of ZrO ₂ added is 0.005 mol % or more. Also,
When the amount of ZrO ₂ added exceeds 10.000 mol %, the dielectric loss angle tan δ increases, the dielectric constant ε gradually decreases, and the nonlinear index α also decreases. Also, the varistor voltage per unit thickness (V _1nA /
mm) becomes a large value when Dy ₂ O ₃ is less than 0.005 mol % because the specific resistance of the sintered body is large. moreover,
Since the specific resistance of the sintered body increases as the total amount of Dy ₂ O ₃ and ZrO ₂ added increases, V _1nA /mm generally takes a large value. Therefore, the range that satisfies both the functions of a varistor and a capacitor at the same time is 0.005 to 10.000 mol % of Dy ₂ O ₃ and 0.005 to 10.000 mol % of ZrO ₂ . Example 2 SrTiO ₃ , Dy ₂ O ₃ and NiO were mixed in the composition ratio shown in Table 2 below, mixed, molded and fired in the same manner as in Example 1, and measured under the same conditions. are shown in Table 2.

【table】

[Table] *...Comparative example As shown in Table 2, the amount of Dy ₂ O ₃ added was 0.005.
It contributes to lowering the resistivity of the sintered body in the range of ~10.000 mol%, and can be used as a varistor by re-firing in air. During sintering, NiO dissolves in crystals mainly composed of SrTiO ₃ or segregates at grain boundaries, increases the resistivity of the grain boundary layer, and contributes to increasing the nonlinearity of the sintered body. It is clear that such an effect appears when the amount of NiO added exceeds 0.0005 mol %, as the nonlinear index α suddenly increases. Furthermore, when the amount of NiO added exceeds 10.000 mol%, the dielectric loss angle tan δ increases, the dielectric constant ε gradually decreases,
The nonlinear index α also decreases, and the characteristics deteriorate. Also, the varistor voltage per unit thickness (V _1nA /
mm) becomes a large value when Dy ₂ O ₃ is less than 0.005 mol % because the specific resistance of the sintered body is large. moreover,
When the amount of NiO added is small, some solid solution is observed in the crystal, and the varistor voltage (V _1nA /mm) decreases. Therefore, the range that satisfies the functions of both varistor and capacitor at the same time is Dy ₂ O ₃ 0.005 to 10.000%,
NiO is 0.005 to 10.000 mol%. In addition, in Examples 1 and 2, the case where only ZrO ₂ and NiO were used alone was explained, but instead of these, Mg, Sn, Sb, W, Bi, Fe
It has been confirmed that similar effects can be obtained even when each of the oxides is used alone in the above-mentioned predetermined amount range. In addition, these Zr, Ni, Mg, Sn, Sb, W, Bi, Fe
It has been confirmed that the same effect can be obtained by using two or more types of oxides in such a manner that the total amount added falls within the above-mentioned predetermined amount range. Using the above elements, we created a circuit as shown in Figure 4, and investigated the output status for noise input A as shown in Figure 5. As a result, we found that the output status curve B in Figure 5 shows I was able to suppress the noise.
In FIG. 5, 7 is an element of the present invention, and 8 is a coil. Note that the output condition of the conventional filter circuit shown in FIG. 1 is as shown by the output condition curve C in FIG. 5, and noise is not removed sufficiently. Further, the conventional filter circuit including the varistor shown in FIG. 2 can obtain an effect similar to the circuit shown in FIG. . Effects of the Invention As described above, the device using the ceramic composition according to the present invention has an unprecedented composite function, and can play the roles of a varistor and a capacitor at the same time. It contributes to simplification, miniaturization, high performance, and low cost, and is useful for absorbing surges in various electrical and electronic devices.
The application can be expanded to noise removal, and its practical value is extremely large.

[Brief explanation of drawings]

1 and 2 are circuit diagrams showing conventional noise filter circuits, FIG. 3 is a cross-sectional view of an element using the ceramic composition of the present invention, and FIG. 4 is a noise filter using the element shown in FIG. 3. FIG. 5 is a circuit diagram showing a filter circuit, and is a characteristic diagram showing the input noise and output noise situations of the present invention and the conventional noise filter circuit.

Claims (1)

[Claims] 1 80.000 to 99.990 mol% of SiTiO ₃ , 0.005 to 10.000 mol% of Dy ₂ O ₃ as a metal oxide for promoting semiconductor formation, selected from the group consisting of Mg, Zr, Sn, Sb, W, Bi, Ni, and Fe. 1. A voltage-dependent nonlinear resistor ceramic composition containing 0.005 to 10.000 mol% of at least one element in the form of an oxide.