JPH0133921B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an oxide semiconductor for a thermistor that has a negative temperature coefficient of resistance and can be used as a temperature sensor at -60°C to 450°C. Structures of conventional examples and their problems Conventionally well-known manganese-cobalt-nickel and manganese-cobalt-nickel-copper oxide thermistor materials have been mainly used as general-purpose disk thermistors, but they cannot be used in high-temperature applications. Because the resistance value fluctuates greatly at low temperatures, it cannot be used at high temperatures exceeding 300℃.
It has been used at temperatures below 300°C. To address this problem, various compositions have already been proposed and implemented. One of the main ingredients is manganese oxide,
We proposed a manganese-nickel-chromium-silicon based oxide semiconductor characterized by containing chromium and silicon (Japanese Unexamined Patent Publication No. 15403/1983). However, it was not possible to obtain a high-resistance material that could be used up to 450°C. OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a thermistor that exhibits an appropriate resistance value at 300°C to 450°C and can be used stably. Structure of the Invention The present invention provides the above-mentioned manganese-nickel-chromium
As a result of further studies on silicon-based oxides, we were able to obtain a material that can be used stably at temperatures between 300°C and 450°C. The oxide semiconductor for thermistor of the present invention has a proportion of manganese of 88.0 to 99.3 atom%, nickel of 0.1 to less than 5.0 atom%, chromium of 0.3 to 5.0 atom%, and silicon of 0.3 to 2.0 atom% in terms of metal elements. The total amount is 100 atomic %. Description of Examples Examples of the present invention will be described below. Commercially available raw materials MnCO ₃ , NiO, Cr ₂ O ₃ and SiO ₂ were blended to have the respective compositions (atomic percentages) shown in the table below. To illustrate the thermistor manufacturing process, these blended compositions were wet-mixed in a ball mill, the slurry was dried and then calcined at a temperature of 800°C, and the calcined product was wet-pulverized and mixed in a ball mill. The resulting slurry is dried, polyvinyl alcohol is added and mixed as a binder, the required amount is taken and pressure molded into disk shapes to make many molded products, and these are sintered in air at a temperature of 1300℃ for 2 hours. Then, electrodes containing Ag as a main component were baked on both sides of these disk-shaped sintered bodies (diameter: about 6.5 mm, thickness: about 1 mm) to obtain ohmic contact. The resistance values at 25°C and 50°C (R ₂₅ °C and R ₅₀ °C, respectively) were measured for these samples, and the resistivity ρ ₂₅ °C at 25°C was calculated from the following equation (1), and the B constant was calculated by (2 ) Calculated using the formula. ρ ₂₅ ℃ = R ₂₅ ℃ × S/d ... (1) (S = electrode area, d = distance between electrodes) B = 8.868 × 10 ³ × logR ₂₅ ℃ / R ₅₀ ℃ ... (2) Furthermore, these Regarding some of the compositions,
After polishing the above disk to a thickness of 300 μm, both sides were
Burn an electrode containing Rt as the main component. After cutting this into a square shape of 500 μm on each side, it was sealed in a glass tube under nitrogen gas. The terminal is taken out via a dumet wire. This glass-encapsulated thermistor
It was left in air at 450°C and the change in resistance was measured after 1000 hours. These results are summarized in the table below.

【table】

[Table] However, samples marked with * are samples for comparison and are outside the scope of the present invention.
be.
Among the comparative samples, samples 1, 2, 3, and 16 have large specific resistances and are not practical. Samples 5, 8, 10, 14,
Samples Nos. 15, 16, 18, 20, 21, 22, and 24 were excluded from the scope of the present invention because their resistance change rate over time at 450° C. was as high as ±5% or more and lacked practical stability. In addition, among comparative samples 9, 11, 12 and 13, the resistance change rate over time satisfies ±5% or less; Public bulletin)
Since this overlaps with the above, it is excluded from the scope of the present invention. However, the amount of Ni is a continuous amount of 0.1 to 5.0 at%,
Although 5.0 atomic % is excluded, the effect is observed at compositions of 0.1 to less than 5.0 atomic %. Although the above sample uses a sample that was dry molded and then fired, a glass-encapsulated thermistor obtained by wet molding may also be used. Alternatively, it may be a bead-type thermistor coated with glass. Furthermore, it is a good method to add other components as necessary to improve the properties. In the examples of the present invention, zirconia boulders were used for mixing raw materials and pulverizing and mixing calcined products. As a result of elemental analysis of the samples (sintered bodies) of the above examples, the amount of zirconium mixed was 0.5 atomic % or less in all samples based on 100 atomic % of the thermistor constituent elements. As mentioned in the configuration, the present invention is a manganese-nickel-chromium-silicon oxide with a composition having high resistivity and mainly containing manganese.
Moreover, it is possible to obtain a highly stable material in the temperature range of 300°C to 450°C. Addition of SiO ₂ exhibits a sintering accelerating effect, making it possible to obtain dense ceramics. It can also be used as a method for controlling specific resistance. Effects of the Invention As can be seen from the above explanation, the oxide semiconductor for thermistors of the present invention has excellent characteristics over time at 300°C to 450°C, and is most suitable for temperature measurement where high reliability is required at high temperatures. Are suitable. That is,
For example, it is possible to provide a thermistor that can be widely used in fields such as microwave ovens and temperature control of oil combustion.

Claims (1)

[Claims] 1 A sintered body containing oxides of manganese, nickel, chromium, and silicon, whose composition ratio in terms of metal elements is 88.0 to 99.3 atom% of manganese, 0.1 to less than 5.0 atom% of nickel, and 0.3 to 5.0 atom of chromium. % and silicon 0.3-2.0 at% (total 100 at%)
An oxide semiconductor for a thermistor, characterized in that: