JPS5990904A - Porcelain composition for voltage nonlinear resistor - 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 The present invention relates to a ceramic composition for a voltage non-linear resistor mainly containing strontium titanate.

It is known that a voltage nonlinear resistor (hereinafter referred to as a varistor) can be produced by forming an insulating layer at the grain boundaries of a titanate semiconductor ceramic.

As this divine barista, he was originally published in Japanese Patent Application Publication No. 57-27
001, Japanese Patent Application Laid-Open No. 57-35303, etc. In the former method -b, oxides such as Mll, 7n, GO, etc. are applied to the surface of the sodium ditanate semiconductor porcelain, and then oxides such as Mll, 7n, GO, etc.
A heat treatment was performed at a temperature of 200°C to 1300°C for 1 hour to form an insulating layer on the crystal grains y- of the semiconductor ceramic. In addition, the latter b is a metal oxide for promoting semiconductor formation, Nb2O5,1-
f1205, WO3, l-8203, Ce 02,
Metal oxides for improving Jζ and voltage/current nonlinear characteristics such as Nd 203, V205, Cr 203, COO1
CU20, Ml) 03, Mll 02 was made gold stone - it is outperforming.

However, the former has M to form an insulating layer.
Oxides such as n, 7n, and C(1) must be added to the semiconductor porcelain, and heat treatment is required to uniformly diffuse the oxides into the grain boundaries of the semiconductor porcelain.
To obtain a varistor with small variation,
Therefore, due to the characteristics of the C varistor, the nonlinear coefficient vl (α) and the threshold voltage (V th)
The disadvantage is that the variation 71 is large.

In addition, the latter is a metal oxide for improving electric current nonlinear characteristics, such as V205, Cr2O3, CuOl(/11
20, MO03, Mn02 contained in the porcelain composition II
1 in a neutral or reducing atmosphere during the production of A.
Because the firing is carried out at a temperature of 350 to 1420°C, these metal oxides become metallized and evaporate, damaging the sintering surface of the firing furnace and further reducing the nonlinear coefficient (α) and 1 ``The drawback was that there were variations in voltage (V th).

Therefore, it is an object of the present invention to provide a varistor that overcomes the above-mentioned drawbacks.

Another object of the present invention is to provide a varistor with a small variation and a good yield. Rina 4) No), the gist of this invention is that Lf titanate 98.5 to 99.87 mol%, aluminum oxide 0,
(+ to 3・(), 5 mol%, semiconducting agent 0.1・～・
This is a ceramic composition for a voltage nonlinear resistor consisting of 1.0 mol%.

The reason for limiting the composition to the above composition range is as follows. If the aluminum oxide content is less than 0.03 mol%, the nonlinear coefficient (α) becomes small, and if it exceeds 0.5 mol%, the threshold voltage (V port 1) becomes too high. Also, if the semiconducting agent is less than 0.17%, the threshold is 111%.
1 voltage (Vtt+) becomes high and exceeds 1 mol %, it becomes difficult to obtain varistor characteristics. Therefore, the amount of C-11tinium butanoate is limited to a range of 418.5 to 99.87 mol%.

Note that the above composition may contain a trace amount of a mineralizing agent such as 5i02.

Further, 'C and other components may be contained to an extent that does not adversely affect the properties.

” - The composition described is 135% in a neutral or reducing atmosphere.
It is fired at 0 to 1400℃ and further heated to 100℃ in a natural atmosphere.
A heat treatment at 0 to 1200°C turns into semiconductor porcelain, and by forming electrodes on the surface of this semiconductor porcelain, a varistor is obtained.

Furthermore, -C as a semiconducting agent is Y20a, La2O3
Rare earths such as Nb2O5,1-21205, W Oa
etc., and if at least one of these is included in the composition, it is acceptable.

Hereinafter, this invention will be described in detail based on examples. An Example 1 t Fl in +3 r”I' i 0FI, 8g
203, a semiconducting agent was prepared, and sea urchins having the composition ratios shown in Table 1 were prepared. 6% of binder was added to Formulation 1311 size, wet mixed, mixed with 1B2 water, granulated, and molded at 10 (1K/cm2).

The molded product was pre-fired at 1150°C in a natural atmosphere, and then fired at 1350-1400°C in a C reducing atmosphere to produce a semiconductor disk porcelain with a diameter of 8 mm and a thickness of 1 mm. Thereafter, heat treatment was performed in a natural atmosphere at 10 to 1200°C.

At this stage, a semiconductor porcelain is obtained in which an insulating layer is formed at the grain boundaries.Next, 6 silver base plate is printed and coated on the surface of the semiconductor porcelain, and it is baked in a natural atmosphere at 8001 (to form a JSC electrode, The threshold voltage J'(V
tb), the non-N line coefficient (α) was determined, and the results are shown in Table 1.

Here, C', threshold fiT] voltage (Vtl+) is the voltage drop when a current of 10 IllA is passed through the varistor, and the nonlinear coefficient (α) was calculated using the following formula J.

a= 1/, (20(1(Vtoll △/V1
n+A) Table 1 [-ゝweight 19 From Table 1, if we take this 5 to the light °b, then a varistor with a large α is used in the region where Vll is low.

In Table 1, those marked with an asterisk (*) are outside the scope of this invention, and the others are within the scope of this invention. In addition, test O'31 No. 9b had a high threshold voltage IF, making it impossible to measure α.

Example 2 Sample number 3 of Example 1; b is Δ, 1ii (J'FI
For each of the 100 samples, V 111 ; (X) average 1ifj (K) was determined, and () the results are shown in the total m2 table.

Next, a pulse voltage of 300 V was applied to each sample Δ,]3, and the average value (also) of Vtll and α was measured after that,
The results are shown in Table 2 as -1B-.

As J3 and Comparative Example, a composition having the following composition ratio was used. (Varistor equivalent to JP-A No. 57-35303) 3 r l-i 03 99.3 mol% Y20
a O, 2 mol% Cll0
0.5 mol% of this composition was mixed with 5% of the binder.
~10 weight% addition, 1L capacity 100 (IK o/c
Semiconductor porcelain was obtained by firing the M2R molded notches at 1400°C in an original atmosphere and then heat-treating them at 100°C in an oxidizing atmosphere. Silver paste I was printed on the surface of this semiconductor porcelain and baked at 800°C. e-firing f・H] (electronic (→A was formed and a varistor was created.

The average value of V[11, α for 100 varistors (
A pulse voltage of 300 V was applied to Sample C) (Nonora), and the average values of Vl, l+, and α were measured (Sample C'''). This result also conforms to Table 2. I showed it separately.

1 J3, Table 2 shows each sample △, Δ-1BXB', C, C
The deviation value (σ) for ′ is also shown.

Table 2 As is clear from Table 2, according to the present invention, the threshold voltage (Vtll) and the nonlinear coefficient (α) vary by 1.
- 1q small varistors are placed.

As is clear from the above examples, a metal oxide is coated and diffused to form a solid layer at the grain boundaries in the ballista ceramic composition according to the present invention. Manufacture is easy because no steps are required, and yields are also good. Furthermore, it is possible to provide a varistor with a small variation in vth and α of 1.

Patent application person Murata Manufacturing Co., Ltd. Procedure Supplementary IR Store (Set 6) % Formula % 2. Name of the invention: Porcelain composition for voltage nonlinear resistor 3. Relationship with the amendment case Address of the patent applicant Kyoto Prefecture Nagaokakyo City Hitogami Knee ■ 26th 10q Name
((i23) Tei I Ill Manufacturing Co., Ltd. February 22B, 1982 (shipping port) 5, number of inventions increased by amendment 7, engraving of details of amendment m (no change in content)

Claims (1)

[Claims] Titanium titanate 98.5-99.87 mol%
, 0.03 to 0.5 mol % of 7-fluminium oxide, and 0.1 to 1.0 mol % of a semiconducting agent.