JPS607703A - Voltage depending nonlinear resistor porcelain composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention produces a voltage-dependent nonlinear resistor (hereinafter referred to as a varistor) that is used for abnormal voltage absorption and noise removal in various electrical and electronic devices. The present invention relates to a voltage-dependent nonlinear resistor ceramic composition suitable for.

Conventional structure and its problems Traditionally, it has been used to absorb abnormally high voltages (hereinafter referred to as surges) and remove noise in various electrical and electronic devices.

SiC varistors and ZnO-based varistors, which have voltage-dependent nonlinear resistance characteristics, have been used to eliminate sparks. The voltage-current characteristics of such a varistor can be approximately expressed as follows.

Knee (v/C) a Here, Δ is the current, ■ is the voltage, C is the risk-specific constant, and α is the 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 6o. 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 risk voltage (e.g. It has little effect on noise, etc.) and has a large dielectric loss angle (tan δ) of 5 to 10%.

On the other hand, in order to remove these noises, the apparent dielectric constant can be reduced to 5×1o by appropriately selecting the composition and firing conditions.
Semiconductor ceramic capacitors with a size of about 4 to 6×10′ and a fan δ of about 1φ are used. However, if a current exceeding a certain limit is applied to the element due to a surge or the like, this semiconductor ceramic capacitor will be destroyed or will 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 The configuration is like this.

FIG. 1 shows a general conventional noise filter circuit, and FIG. 2 shows a conventional noise filter circuit configured by combining a varistor, a capacitor, and a coil. 1 is a coil, 2 is a capacitor, 3 is a barista.

However, the configuration shown in FIG. 2 has the drawbacks of increasing the number of parts inside the device and contradicting the trend toward miniaturization of devices. We have created a porcelain composition that is suitable for making a varistor that has the functions of both a varistor and a capacitor, and has the combined functions of surge absorption and noise removal with one element, eliminating the drawbacks in surge absorption and noise removal. The purpose of the offer is to make money.

Structure of the Invention In order to achieve the above-mentioned objects, the present invention provides 5rTi
05, Nb2O5 and Ta205 as metal oxides for promoting semiconductor formation, and MnO2 and Na as additives.
K.

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 Ca, CA, In, Ba, and Pb.

Description of examples The present invention will be specifically described below with reference to Examples.

5rTi03 and Nb2O5, Ta205 and MnO2,
After weighing BaO so as to have the composition ratio shown in the table below, the mixture is wet mixed using a ball mill or the like for 6 hours, dried, and then calcined in air at 1QOo to 1260°C for 1 to 5 hours. After that, it was wet-pulverized for 4 hours using a ball mill, etc., dried, and then granulated with 8 wt% of an organic binder (ψ1, e.g., polyvinyl alcohol).
8. (Bill φ
It was baked at 450°C for 1 to 6 hours. Thus obtained tl,
The specific resistance of the ft fired body was 0.1 to 0.8 Ω·cm, and the average grain size was 20 to 6011 m. Next, this sintered body was fired in air at 1000 to 1300°C for 0.5 to 6 hours to obtain the sintered body 4 shown in FIG. Furthermore, both halves of the sintered body 4 are polished with an abrasive such as SiC.

Electrodes 5 and 6 were formed using a conductive metal such as Ag.

The diameter of the electrodes 6, 6 is 5. □　mmφ.

The characteristics of the device thus obtained are also shown in the table below.

(Margin below) Here, the evaluation of the characteristics of the element as a varistor is as described in L7 above.
This can be done using α and C in the voltage-current characteristic formula (% formula %) (where ■ is current, ■ is voltage, C is a constant unique to the varistor, and α is a nonlinear index). However, since accurate measurement of C is difficult, in the present invention, the varistor voltage per unit thickness (hereinafter V1mA/m
y).

α= 1/log(V+omA/ff+mA)
Characteristics as a varistor are evaluated based on the value of (rc, %vIOmA is the varistor voltage when a varistor current of IQmA is applied, and V+mA is the varistor voltage when a varistor current of 1 mA is applied). -! , f? Characteristics as a co capacitor are evaluated using the dielectric constant ε and the dielectric loss angle tan δ at a measurement frequency of 1 kHz. The above data is based on the firing temperature of 1400℃ for 2 hours in a reducing atmosphere.
, 2 hours, firing temperature in air 1200℃ for 2 hours, 3
It was done in time.

As mentioned above, Nb2O5 and Ta205 form a solid solution in the crystal mainly composed of 5rTi05 during reduction firing, and the resistivity of the sintered body can be lowered to around 1.0Ω・a by atomic side splitting. Therefore, by re-firing in air, a high resistance layer is formed at the grain boundaries of the sintered body, which exhibits varistor characteristics.

``!I'c, Nt) 205 is contained mixedly in TiO2 in the raw material, and usually contains 0.001 to 0.200 mo#% in the industrially refined raw material. Contains 1 liter.Nb
If 5rTi05 is made into a semiconductor using only 2O5, the specific resistance will be a little high! Although it exhibits l1% varistor characteristics, the characteristics are unstable. However, when Ta205 is added to Nb2O5, the resistivity can be lowered and stable characteristics can be obtained. If the amount of Ta205 added is too large, it will inhibit the solid solution of other additives; o○1~5. OOO mole ratio is appropriate.

When MnO2 is added, the material exhibits varistor characteristics, but the dielectric constant becomes small and the tan δ becomes large.

However, when BaO is added at the same time, both α and dielectric constant become large, and tan δ becomes small, so that the characteristics are significantly improved.

As the amount of MnO2 added increases, tan δ increases.

Since the properties deteriorate, a 0.001 to 2.000 molar ratio is appropriate.

The dielectric constant of BaO decreases as the amount added increases, so
A suitable molar ratio is 0.001 to 2.000.

Therefore, the sintered body obtained within the above composition range can function as both a varistor and a capacitor.

In addition, although the case where only BaO was used alone was explained in the Example, instead of this, Ca was used.

It has been confirmed that similar effects can be obtained by using oxides of Cd, In, Ba, and Pb, each with n alone, within the above-mentioned predetermined amount ranges. Also, these Ba, (a, Cd, I
n.

It has been confirmed that similar effects can be obtained even when two or more types of Ba and Pb oxides are used in such a manner that the total amount added falls within the above-mentioned predetermined amount range.

Create a circuit as shown in Figure 4 using the above elements,
As a result of examining the output status of the noise input cam shown in FIG. 5, it was found that the noise could be suppressed as shown in output status curve B in FIG.

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. 6, and noise is not removed sufficiently. The conventional filter circuit including the varistor shown in FIG. 2 can achieve an effect similar to the circuit shown in FIG. .

Effects of the Invention As mentioned above, the device using the ceramic composition of the present invention has multiple functions that have not been seen before. It simplifies, contributes to miniaturization, high performance, and low cost, and absorbs surges in various electrical and electronic devices.

It can be extended to noise removal, and its practical value is extremely large.

[Brief explanation of drawings]

Figures 1 and 2 are circuit diagrams showing conventional noise filter circuits, Figure 3 is a cross-sectional view of an element using the ceramic composition of the present invention, and Figure 4 shows the element of Figure 3. FIG. 5 is a circuit diagram showing the noise filter circuit used, and a characteristic diagram showing the input noise and output noise conditions of the present invention and the conventional noise filter circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2 Figure 3, 5 Figure 4 Figure 5 All liquid damage 2

Claims (1)

[Claims] 5rTiO3 is 99.996-90. EjOOmo#%,
0.00 Nb2O5 as a metal oxide for promoting semiconductor formation
1-0-200 mol%% Ta205, Oo1-5.
Contains ooo mole, 0.001 to 2.000 mol% in Mnt-MnO2 (7) form, Na, K, C
Na2O at least one element selected from the group consisting of a, Cd, In, Ba, and Pb. K2O, CaO, CdO, In20B, BaO, P
A voltage-dependent nonlinear resistor ceramic composition characterized in that it contains 0.001 to 2.000 molti in bOO form.