JPH0582312A - Composition for thermistor - Google Patents

Abstract

PURPOSE:To provide a composition for a thermistor which has a small resistance change rate by the use at a high temperature, high humidity and high reliability and is made of manganese-nickel-chromium series oxide. CONSTITUTION:0.01-10wt.% of zirconium oxide is added to oxide in which 15-55 mole % of manganese, 15-85 mole % of nickel and 0.01-30 mole % of chromium by ratio of only metal elements in such a manner that the total sum becomes 100 mole %, thereby constituting a composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a thermistor, and its resistance value changes from that before being placed in a high temperature and high humidity atmosphere even after passing through a high temperature and high humidity atmosphere (hereinafter This relates to a composition for a thermistor having a small resistance change rate under high temperature and high humidity use.

[0002]

2. Description of the Related Art Conventionally, as a thermistor composition comprising an oxide semiconductor containing manganese oxide as a main component, a composition containing manganese, nickel and chromium is known.

Further, these thermistor compositions cannot be used when used at a high temperature such as 300 ° C. or higher, and therefore cannot be used. Therefore, in order to solve these problems, manganese, nickel and chromium are used. By adding zirconium oxide to the system oxide spnel,
It has been proposed that it can be used stably even at a high temperature of 0 ° C. or higher (see, for example, JP-A-60-22302).

[0004]

However, manganese-
In the thermistor composition comprising an oxide of three metal elements of nickel-chromium, or a known thermistor composition obtained by adding a certain amount of zirconium oxide to the composition,
There is a problem that the rate of change in resistance under the use of high temperature and high humidity is large.

Therefore, an object of the present invention is to provide a composition for a thermistor comprising a manganese-nickel-chromium oxide having a small resistance change rate under use at high temperature and high humidity.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have made earnest studies, and as a result, the ratio of only metal elements was 15 to 55 mol% of manganese, 15 to 85 mol% of nickel, and 0.01% of chromium. Zirconium oxide is added to an oxide of 100 mol% to 30 mol% and 0.01 to 1 mol% of zirconium oxide.
It has been found that the above problem can be solved by adding 0% by weight.

[0007]

By using the composition for a thermistor having the composition of the present invention, the rate of change in resistance under the use of high temperature and high humidity can be remarkably reduced as compared with the conventional one.

[0008]

EXAMPLES Examples of the present invention will be described. Commercially available trimanganese tetraoxide, nickel oxide, chromium oxide, and zirconium oxide are weighed and blended so that the composition after sintering will be the compositions shown in Tables 1 and 2 below, and wet mixed in a ball mill for 16 hours.
These commercially available raw materials are Fe, Si, Na, K,
It contains a small amount of metal compounds such as Ca.

After that, it is dehydrated and dried, and powdered using a mortar and pestle. Next, put this powder in an alumina bowl and
Preliminary calcination at 1200 ° C. for 2 hours. The calcined product is finely pulverized with a ball mill, dehydrated and dried, polyvinyl alcohol (PVA) is added as a binder, and granulated into granules with a mortar and pestle, and then pressed into a disc shape with a diameter of 16 mm and a thickness of 2.5 mm. Mold.

Next, after heating at 600 ° C. for 2 hours in the atmosphere to remove the binder, 1000 ° C. to 140 ° C. in the atmosphere.
A sample is obtained by carrying out a main firing at 0 ° C. for 2 hours. A silver paste is screen-printed on both sides of the obtained sample and baked at 800 ° C. to form an electrode.

Each completed sample was subjected to direct current 4-terminal method,
Resistance value of 25 ℃ (R25), resistance value of 85 ℃ (R85)
Was measured and the specific resistance (ρ
25) and the B constant (B25
/ 85) was calculated and the results shown in Tables 1 and 2 below were obtained.

Further, each sample was put in boiling pure water at 100 ° C., and the resistance value (R25 ′) was measured after boiling for 50 hours, and the initial resistance value (R25) at 25 ° C. was calculated by using the following mathematical formula 3. The rate of change in resistance (ΔR25) was calculated, and the results are shown in Tables 1 and 2 below.
The results shown in are obtained.

[0013]

[Equation 1] However, ρ25: specific resistance at 25 ° C (Ω · cm) S: electrode area (cm ² ) t: thickness of sample (cm) R25: resistance value at 25 ° C (Ω)

[0014]

[Equation 2] However, B25 / 85: B constant (K) R25: Resistance value at 25 ° C (Ω) R85: Resistance value at 85 ° C (Ω)

[0015]

[Equation 3] Where ΔR25: resistance change rate (%) after boiling test R25 ′: resistance value after boiling test (Ω) R25: resistance value before boiling test (Ω)

[0016]

[Table 1]

[0017]

[Table 2]

In Tables 1 and 2, Sample Nos. 1, 2, 3, 4, 5, 13, 14, 17, 17 marked with X are shown.
8, 19, 22, 23, 24, 27, 28, 29, 3
3, 34, 35 and 39 are composition ratios outside the range of the present invention, and these have ΔR25 of more than 5.0%, and there is a problem in reliability in practical use, but comparison with the composition of the present invention. Written for.

As is apparent from Tables 1 and 2, the composition of the present invention has a ρ25 of 5415 to 1.35 × 10 ⁶ Ω · cm, B
25/85 is in the range of 3936 to 4597K which is practically sufficient, and ΔR25 is very small and stable at 1.7 to 5.0%.

Next, the reason for the range of numerical limitation will be described. When the ratio of manganese is less than 15 mol%, ΔR2
5 exceeds 5%, which makes it unsuitable for use under high temperature and high humidity (see, for example, Sample Nos. 4 and 5 in Table 1).

On the other hand, when the ratio of manganese exceeds 55 mol%, ΔR25 also exceeds 5% (see Table 1 for example).
No. 1, No. 2). Next, when the proportion of nickel is less than 15 mol%, ΔR25 exceeds 5% (for example, see Sample No. 2 in Table 1).

When the proportion of nickel exceeds 85 mol%, the sinterability is extremely deteriorated, and the fired body is not suitable for a thermistor. When the chromium content is less than 0.01 mol%, ΔR
25 exceeds 5.0% (Sample No. 30, 4 in Table 2)
(See 0 for comparison). When the ratio of chromium exceeds 30 mol%, ΔR25 exceeds 5% (for example, sample No. 3, Table 1).
4).

When the ratio of zirconium oxide as an additive is less than 0.01% by weight based on the main component, ΔR25 is 5%.
(For example, samples Nos. 13, 14, 18, in Table 1
19, 23, 24, sample Nos. 28, 29, 34 of Table 2
35).

Further, when the ratio of zirconium oxide exceeds 10% by weight with respect to the main component, ΔR25 also exceeds 5% (for example, Sample No. 17, 22, 2 in Table 1).
7, see Sample No. 33, 39 in Table 2).

[0025]

According to the present invention, by adding an appropriate amount of zirconium oxide to a composition containing manganese, nickel and chromium oxides having a certain composition as a main component, the resistance change under high temperature and high humidity use can be improved. A highly reliable thermistor composition having a very low rate can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazushi Saito 1-13-1, Nihonbashi, Chuo-ku, Tokyo Inside T-DK Co., Ltd. (72) Keiichi Kato 1-1-13-1, Nihonbashi, Chuo-ku, Tokyo No. T-Day-K Co., Ltd.

Claims (1)

[Claims] 1. The ratio of only metal elements is 15 to 20% manganese.
55 mol%, nickel 15-85 mol%, chromium 0.01
A composition for a thermistor, characterized in that 0.01 to 10% by weight of zirconium oxide is added to an oxide consisting of ˜30 mol% and the total amount of which is 100 mol%.