JPH0578921B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing an oxide semiconductor for a medium to high temperature thermistor that can be used at 200°C to 500°C. Conventional structure and its problems Conventionally well-known Mn-Co-Ni-Cu
Oxide-based thermistor materials have been mainly used as general-purpose disk-type thermistors, but they cannot be used at temperatures exceeding 300°C because their resistance values fluctuate significantly when used at high temperatures. It has been used at the following temperatures: Meanwhile, 700℃~1000
Materials that can be used at high temperatures of ℃ 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. 16895-1980, Japanese Patent Publication No. 33756-1983). However, these oxide materials also require firing at a high temperature exceeding 1600°C, and cannot be fired using an ordinary electric furnace (maximum 1600°C). Furthermore, even in the case of sintered bodies of these oxides, the resistance value changes significantly over time, and even those that are extremely stable have a resistance value of 10%.
(after 1000 hours), and there was a problem with stability over time. In addition, the demand for thermistors with excellent stability at temperatures between 200°C and 500°C has increased in the sensor market, and thermistor materials that meet this demand {Mn-Ni-Al oxide system: JP-A No. 57-95603, ( Ni _x Mg _y Zn _z )
Mn ₂ O ₄ spinel system: JP-A-57-88701,
(Ni _p Co _g Fe _r Al _s Mn _t ) O ₄ spinel system: JP-A-57-
Publication No. 88702, etc.] have been proposed, but they are still in the evaluation stage. In response to the above request, the inventor also
Mn-Ni-Cr-Zr oxide system (patent application 1987-131265)
No.) was proposed. Purpose of the invention The present invention has been made in view of the above problems, and
The purpose is to provide a method for producing an oxide semiconductor for a thermistor that exhibits an appropriate resistance value even at 300°C to 500°C and can be stably used. Structure of the Invention In order to achieve the above object, the method for manufacturing a thermistor oxide semiconductor of the present invention includes the steps of:
Using manganese, nickel, chromium, and stabilized zirconia containing lanthanum oxide as starting materials, mixing,
A method for producing an oxide semiconductor for a thermistor by firing. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Commercially available raw materials MnCO ₃ , NiO, Cr ₂ O ₃ and Mn ZrO ₂ containing 3 mol of La ₂ O ₃ provided by the manufacturer:
They were blended so that Ni:Cr:Zr=76.0:2.0:2.0:20.0 atomic%. To illustrate the thermistor manufacturing process, these blended compositions were wet mixed in a ball mill, the slurry was dried and calcined at 1000°C, and the calcined product was wet-pulverized and mixed again in a ball mill. After drying the obtained slurry, add and mix polyvinyl alcohol as a binder, take the required amount and make a 30mm
Form into a block of 〓×15mm ^t . This molded body
It was fired in air at 1400°C for 2 hours. The blocks obtained in this way are then sliced and polished to reduce the thickness.
A 150-400 μm wafer is taken out and platinum electrodes are provided by screen printing. This electroded wafer is cut into chips of desired dimensions. This element is sealed in a glass tube in argon gas or air and hermetically isolated from the outside air. The thermistor sensor manufactured in this way
The rate of change in resistance value over time at 500°C is shown in the graph of the drawing by solid line 1. In addition, for comparison, the graph also shows the resistance value change rate over time of the thermistor sensor using the already proposed Mn-Ni-Cr-Zr oxide material as the dashed line 3, which is the same as this example. Broken line 2 shows the rate of change in resistance value over time of a sensor obtained through the same manufacturing process using zirconia and lanthanum oxide instead of stabilized zirconia as raw materials. Note that the dimensions of the element used in the sensor are 400 μm x 400 μm x 300 μm. Initial resistance value of sensor at 25℃ and 300℃
The thermistor constant B determined from the resistance values at two points at 500°C is also shown in the following table.

[Table] As is clear from the graph, according to the manufacturing method of the present invention, compared to samples No. 2 and No. 3,
It has particularly excellent stability at high temperatures. Focusing on the microstructure of the sample, the stabilized zirconia containing lanthanum oxide does not form a solid solution in the Mn-Ni-Cr-based oxide spinel crystal, but exists as a joint between the crystals or as the crystal grain itself. On the other hand, those containing La ₂ O ₃ and ZrO ₂ at the same time,
ZrO ₂ still exists in the joints of spinel crystals or as crystal grains themselves, but La is not preferentially dissolved in ZrO ₂ but is almost uniformly dispersed throughout the sintering process. This was revealed through X-ray microanalysis of body cross sections. Further, even by X-ray diffraction, it was not possible to identify the Mn-Ni-Cr-La based oxide. In this case, the sensor was created by enclosing an element cut out from a block, but it is also possible to use a bead type element, and there are no restrictions on the sensor manufacturing method. The stabilized zirconia used in this example was obtained by a coprecipitation method using oxalate as a starting material, and the composition range is currently under consideration. 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 sample (sintered body) of the above example, the amount of Zr mixed was 0.5 atomic % or less based on 100 atomic % of the thermistor constituent elements. In addition, when using agate cobblestone, the amount of Si mixed in is
It was less than 1.0 at%. Effects of the Invention As explained above, if the method for manufacturing an oxide semiconductor for a thermistor of the present invention is used, it is possible to
It is possible to obtain a temperature sensor with a small change in resistance value over time in the temperature range of ℃, and high reliability is required at high temperatures. For example, it can be expected to contribute to application fields such as temperature control in microwave ovens and oil burners.

[Brief explanation of the drawing]

The drawing is a graph showing the resistance value change characteristics over time of a glass-encapsulated thermistor.

Claims (1)

[Claims] 1. Manganese,
A method for producing an oxide semiconductor for a thermistor, which comprises mixing and firing stabilized zirconia containing nickel, chromium, and lanthanum oxide.