JPS59208809A - Voltage temperature dependency 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 Field of Industrial Application The present invention relates to a positive pressure dependent nonlinear resistor (hereinafter referred to as a varistor) 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 making.

Conventional configurations and their problems Conventionally, SiC has been used in various electrical equipment and electronic equipment to absorb abnormally high voltages (hereinafter referred to as surges), remove noise, eliminate sparks, etc. Ballista and ZnO-based materials were used. The voltage-current characteristics of such a varistor can be approximately expressed as follows.

I-(V/C)a Here, ■ is a current, ■ is a voltage, C is a constant specific to the varistor, and α is a voltage nonlinear index.

The σ of SiC varistors is about 2 to T, and it can be as high as 50 for ZnO-based varistors. Although such /〈risk has excellent performance in absorbing relatively high voltages such as surges, it has a low dielectric constant and a small specific capacitance, so
It has little effect on absorbing low voltages (such as noise) below the varistor voltage, and the dielectric loss angle (
11δ) is also thick, with a ratio of 5 to 10.

On the other hand, to remove these noises, the apparent dielectric constant can be reduced to 5X10 by appropriately selecting the composition and firing conditions.
Semiconductor ceramic capacitors with a lan δ value of around 1 coefficient 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 may break down or cease to 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 (coils) for purposes such as surge absorption and noise removal. The noise filter has this structure.

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.
is a coil, 2 is a capacitor, and 3 is a varistor.

However, the configuration shown in FIG. 2 has disadvantages in that it increases the number of parts inside the device and 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 device that has both risk and capacitor functions and can perform surge absorption and noise removal with a single element. Our goal is to provide a complete range of porcelain compositions that are suitable for making risk-free products.

Arrangement of the Invention To achieve this object, the present invention 1d, 5rTi0
5 and.

A trace amount of Nb2O5 that is present in the raw material from the beginning, Ta205, Na, and K as metal oxides for promoting semiconductor formation.

To obtain a voltage-dependent nonlinear resistor ceramic composition containing a predetermined amount of at least one element selected from the group consisting of Ca, (d, In, Ba, and Pb). It is.

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

<Example 1> 5rTi03 and a trace amount of Nb205 present in the raw material from the beginning (Nb2O in the raw material used in this implementation ψ1)1
5 (content: 0.050 mol%), Ta205 as a metal oxide for promoting semiconductor formation, and CdOi as an element for improving nonlinearity. After wet mixing and pulverization for 6 hours, drying, and calcining in air at 1000° C. for 4 hours. After that, it is wet-pulverized for 4 hours using a ball mill or the like, dried, and then an organic binder (such as polyvinyl alcohol) f! : After adding 8 wt% and granulating, 8
．． 0φ (mm) x 1. The molding pressure was about 1. Pressure molding was performed at ot, /aA. This molded body was fired at 1350'C for 4 hours in a total reducing atmosphere (for example, N2:N2 = 121 + flow rate 1.0 l/m1n). The specific resistance of the fired body thus obtained is 0.3 on average.
The average particle size was 30 μm in Ω-cm, and then
The above fired body was fired in air at 1300°C for 2 hours,
A sintered body 4 as shown in FIG. 3 was obtained. Furthermore, both surfaces f of the sintered body 4 are polished using an abrasive such as SiC, and the polished surfaces are
Electrodes 6, 6 were formed using a conductive metal such as G. The shape of the electrodes 6, 6 was 6, ○φ (circular).

The characteristics of the device thus obtained with t' are also shown in Table 1.

In addition, characteristic evaluation of the element as a varistor 1d-1 series of voltage-current characteristic formulas (% formula %) (where I is current, ■ is voltage, C is), a risk-specific constant, and α is a nonlinear index. . ) can be done by α and C in ).

However, since accurate measurement of C is difficult, in the present invention, the value of the varistor voltage per unit thickness (hereinafter referred to as V1mA/mm) when a current of 1 mA is passed, and (1
= 1 /log (■10 mA / ■+ mA)
(However, VlomA is the varistor voltage when a current of 10 mA is applied, and VlmA is the varistor voltage when a current of 1 nlA is applied.) Characteristics as a varistor are evaluated based on the value. Further, the characteristics as a capacitor were evaluated using the dielectric constant ε and the dielectric loss angle tan δ at a measurement frequency of 1 kHz.

As shown in Table 1, the addition amount of Ta205 is 0.00.
When the molar ratio exceeds 6, it becomes a solid solution in the lattice of the crystal mainly composed of 5rTi05f during sintering, and the total resistivity of the sintered body decreases to 1. Since it is possible to lower the resistance to around oΩ-on, by re-firing in air, a resistive layer is formed at the grain boundaries of the sintered body, and it can be used as a varistor. However, if Ta205 exceeds 10,000 mol%, it will no longer form a solid solution, and the specific resistance of the sintered body will increase, making it unsuitable for use as a varistor.

In addition, N1) 20stlj is contained mixed in TiO2 in the raw material, and although it was not intentionally added as an additive, the presence of Nb2O5 does not inhibit semiconductor formation. , TiO2f as raw material
: Contains Nb2O5 even if it is not purified to high purity'! =
It is safe to use it in condition 2.

Note that the content of Nb2O5 varies depending on the purification purity of TlO2, but usually 0.00
Since 1 to 0.200 mo#% of Nb2O is contained, the content of Nb205 was set to 0.001 to 0.200 mole φ.

C (10) segregates at the grain boundaries of crystals mainly composed of SrTiO5f during firing, and increases the total resistivity at the grain boundaries.

This contributes to increasing the nonlinearity index a of the sintered body.

This effect appears when the amount of CdO added is 0.
This is when the number of moles reaches 42. 1. If the amount of CdO added exceeds 10.000 moles φ, the electrical characteristics will deteriorate.

Therefore, the composition range that satisfies both the functions of a varistor and a capacitor is Ta205 of 0.005 to 10.0.
00 molar ratio, C (1075:0.005-10.000
It is mole%. In addition, samples f1~5, 10, 11゜16
．． Nos. 17, 22, 23, and 28 to 34 are comparative examples.

<Example 2> 5rTi03 and a trace amount of N present in the raw material from the beginning
b2O5 (Nb2O5 content in the raw material used in this Example 2 is 0.050 mol), Ta205 as a metal oxide for promoting semiconductor formation, and BaOf as an element for improving nonlinearity as in Example 1 above. Di-molding, reduction firing, and gold oxidation were performed by the following operations. The characteristics of the device thus obtained are shown in Table 2 below.

As shown in Table 2, the amount of Ta205 added is ○, 00
When the molar ratio exceeds 5, it forms a solid solution in the lattice of the crystal mainly composed of 5rTiO5e during firing, and the specific resistance of the sintered body increases to 10Ω due to the valence side. Since the Cm can be lowered to around 100%, a high resistance layer can be formed at the grain boundaries of the sintered body by re-firing in air, and it can be used as a varistor.

However, if Ta205 exceeds 10.000 mol % of gold, it will no longer form a solid solution, and the specific resistance of the sintered body will increase, making it unsuitable for use as a varistor.

In addition, Nb2O5 is mixed and contained in TlO2 in the raw material.
Although it was not intentionally added as an additive, the presence of %Nb2O5 does not inhibit semiconductor formation, so Nb2O5 as a raw material does not need to be purified to a high purity. It is okay to use it in the state of 11 containing it.

The content of Nb2O5 varies depending on the purification purity of TlO2, but it is usually found in industrially refined raw materials. :, is 0
・Contains 001 to 0.200 moles of Nb2O5, Nt)20577) Content is 0.001 to o,
20omol% and soybean.

BaO segregates at grain boundaries of crystals mainly composed of SrT 05 during firing, increases the resistivity at grain boundaries, and contributes to increasing the nonlinear index α of the sintered body.

This effect appears when the amount of BaO added is 0.
This is when it reaches 0.005 molti or more. 'Furthermore, if the amount of BaO added exceeds 10.000 mol%, the electrical characteristics will deteriorate.

Therefore, the composition range that satisfies both the functions of a large star and a capacitor at the same time is Ta205 of 0.005 to 10.0.
000 mo/l/%, BaO is 0.005 to 10. ○○○
The mole is φ. In addition, sample names 1 to 5, 10, 11゜16
．． Nos. 17, 22, 23, and 28 to 34 are comparative examples.

In addition, in Examples 1 and 2, the case where only C1dO and BaO were used alone was explained, but N? It has been confirmed that the same effect can be obtained even if oxides of L, 0, In, and Pb are used alone in the above-mentioned predetermined amounts. 1. In addition, these G6. Ba
, Na, K, Ca, In, Pb oxides
It has been confirmed that similar effects can be obtained even when the total amount added is within the predetermined range mentioned above.

Build the entire circuit shown in Figure 4 using the above elements,
As a result of investigating the output situation for the noise human power A shown in FIG. 5, it was determined that the noise should be suppressed as shown in the output situation curve B in FIG.

In FIG. 5, 7 is the element of the present invention, 8i1''1 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 the noise 2 is not removed sufficiently. 1 fc, shown in FIG. 2 /< A conventional filter circuit including an IJ star can achieve an effect similar to the circuit of FIG. You will get more points.

Effects of the Invention As described above, the element using the ceramic composition of the present invention has an unprecedented multi-functionality and can simultaneously play the roles of a varistor and a capacitor, and can completely replace the conventional noise filter circuit. It is intended to contribute to simplification, miniaturization, high performance, and cost reduction, and is a powerful absorber for various electrical and electronic devices.

If it can be extended to noise removal, its practical value will be extremely large.

[Brief explanation of the drawing]

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 is a noise filter using the element shown in Figure 3. FIG. 6, a circuit diagram of the filter circuit, is a characteristic diagram showing the input noise and output noise conditions of the noise filter circuit of the present invention and the conventional noise filter circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Figure Crocodile Figure 3 Figure 4 Figure 5 → Rotating floor 'j'J, t-mtyr)

Claims (1)

[Claims] 5rTi03 t 99.989~9.800 mol%, Nb2O5 0.001~0.200 mol%, Ta2
05 f 0.006-10.000 mo/l/%, N
a, K, Ca, Cd, In, Ba, Pb in the form of a total oxide of at least one element selected from 0. A voltage-dependent nonlinear resistor ceramic composition characterized by containing 0.05 to 10.000 molar proportions.