JPH043644B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an oxide semiconductor for medium to high temperature thermistors that can be used at temperatures of 200 to 700°C. Conventional structure and problems The well-known Mn-Co-Ni oxide thermistor material has been mainly used as a general-purpose disk-type thermistor, but its resistance value fluctuates significantly when used at high temperatures. Therefore, it cannot be used at temperatures exceeding 300°C, and has been used at temperatures below 300°C. On the other hand, materials that can be used at high temperatures of 700 to 1000°C include stabilized zirconia (ZrO ₂ −Y ₂ O ₃ , ZrO ₂ −CaO, etc.), Mg−Al−Cr−
Fe oxide spinel systems, etc. have been developed (Japanese Patent Publication No. 48-705, Japanese Patent Publication No. 49-63995, Japanese Patent Publication No. 50-16894, Japanese Patent Publication No. 50-16895, Japanese Patent Publication No. 1982-33756). Publication No.). However, these oxide materials also require firing temperatures exceeding 1,600°C, and cannot be fired using an ordinary electric furnace (maximum of 1,600°C). Furthermore, even in the case of sintered bodies of these oxides, the change in resistance value over time is large, and even the most stable ones are only about 10% (after 1000 hours), which poses problems in stability over time. In addition, the demand for thermistors with excellent stability at 200 to 700°C has increased in the sensor market, and thermistor materials that meet this demand {Mn-Ni-Al oxide system: JP-A-57-95603, Nix Mgy Znz)
Mn ₂ O ₄ spinel system; JP-A-57-88701;
(Nip Coq Fer Als Mnt) O ₄ spinel system: JP-A-57-88702, etc. has been proposed, but it is still in the evaluation stage. Purpose of the invention The present invention has been made in view of the above problems, and
The purpose is to provide an oxide semiconductor for a thermistor that exhibits an appropriate resistance value at 200 to 700°C and can be stably used. Structure of the Invention The oxide semiconductor for thermistor of the present invention contains 28.3 to 33.25 atom% of zinc (Zn), 20.0 to 51.7 atom% of manganese (Mn), 15.0 to 46.7 atom% of chromium, and 0.05 to 5.0 atom% of nickel as metal elements. Contains 4 types of metal elements, and the total of these 4 types of metal elements is 100 atomic%
It further contains 0.01 to 10.0 at % of zirconium (Zr) in terms of the composition ratio having the above. Here, the composition is Znv Niw Mnx Cry O ₄ +
z ZrO ₂ can be expressed as V+W+X+Y
= 1, Z is 0.0001≦Z≦0.1. In other words,
The main component of each cation distribution is [Znv ²⁺ (Mn ²⁺ , Mn ⁴⁺ )×Niw ²⁺ Cry ³⁺ ]O ₄ with a spinel-type structure;
It has a ceramic microstructure in which ZrO ₂ or Zr-Mn oxide is mixed. Materials within the above composition range have extremely stable characteristics compared to conventional materials, with a change in resistance value over time at 500° C. for 1000 hours within about ±5%. Description of Examples Examples of the present invention will be described below. First, commercially available ZnO, NiO, MnCO ₃ , Cr ₂ O ₃ , ZrO ₂
were blended to have the respective atomic % compositions shown in Table 1 below. Here, ZrO ₂ is added in proportion to the four components. This is mixed in a ball mill, dried, and calcined at 1200°C. This is ground again in a ball mill and the resulting slurry is dried. After drying this slurry, add and mix polyvinyl alcohol as a binder, take the required amount and
Form into a block of mmφ x 15mmt. This molded body is fired at 1500° C. for 4 hours, and the sintered body is further heat-treated using a hot isostatic pressing device. The blocks obtained in this way are sliced and polished to a thickness of 150~
A 400 μm wafer is taken out and platinum electrodes are provided by screen printing. This electrode-attached wafer is cut into chips of desired size. Leads are attached to this element, and it is further sealed off from the outside air by immersing it in glass. Regarding each composition ratio of the thermistor material manufactured in this way
Resistance value at 500℃, thermistor constant and 500
The rate of change in resistance value over time at °C is also shown in Table 1 below. The chip shape of the sample is 400μ
m×400μm×150μmt.

【table】

[Table] Samples 1, 6, 9, 12, 16, 17, and 18 in the table were placed outside the range because their resistance values changed significantly over time. That is, the composition range defined in the claims of the present invention satisfies the change in resistance value over time within ±5%, as described above, and was determined from a practical standpoint. For this sample, we used a glass-dipped element made of a chip cut from a sintered body block, but we also obtained similar results when we created a bead-type element with the same material composition and encapsulated it in glass. However, in manufacturing bead-type elements, it is necessary to take measures to reduce fluctuations in resistance value. In addition, in the examples of the present invention, agate boulders were used for mixing the raw materials and pulverizing and mixing the calcined product. Also,
As a result of elemental analysis of the samples (sintered bodies) of the above examples, it was found that the contamination of glass forming elements such as Si and B was less than 1 atomic % in all samples relative to 100 atomic % of the thermistor constituent elements. Ta. Effects of the Invention As can be seen from the above examples, the oxide semiconductor for thermistor of the present invention has extremely stable characteristics at high temperatures compared to conventional products, and is suitable for temperature measurement where high reliability is required at high temperatures. It can be said that it is the most suitable. That is, it can be expected to contribute to fields of application such as microwave ovens, temperature control for oil vaporization, and safety devices.

Claims (1)

[Claims] 1 Contains 28.3 to 33.25 at% of zinc, 20.0 to 51.7 at% of manganese, 15.0 to 46.7 at% of chromium, and 0.05 to 5.0 at% of nickel as metal elements, 4
Zirconium is 0.01 to 10.0 at% in proportion to the total composition ratio of 100 at% of metal elements.
Contains oxide semiconductor for thermistor.