JPS61168205A - Manufacture of oxide semiconductor for thermistor - 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 (Field of Industrial Application) The present invention relates to a method for manufacturing an oxide semiconductor for a thermistor for medium to high temperatures that can be used at temperatures from 200°C to 500°C.

(Conventional structure and its problems) The well-known Mn-Co-Ni-Cu oxide thermistor material has been mainly used as a general-purpose disk-type thermistor, but its resistance under high-temperature use is Since the value fluctuation is large, it cannot be used at temperatures exceeding 300°C, so it has been used at temperatures below 300°C.

On the other hand, stabilized zirconia (ZrO□-Y203HZr
O2-CaO, etc.), Mg-Aid-Cr-Fe oxide spinel systems, etc. have been developed (Japanese Patent Publication No. 4B-705, Japanese Patent Publication No. 49-63995, Japanese Patent Publication No. 1984-16).
(Japanese Patent Publication No. 894, Japanese Patent Publication No. 16895-1980, Japanese Patent Publication No. 33756-1987).

However, these oxide materials must also be fired at a high temperature of over 1,600°C, and cannot be fired in an ordinary electric furnace (up to 1,600°C).
00°C), it could not be fired. Moreover, 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% (1000%).
), 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 a thermistor material that can handle stiffness [Mn-Ni-Al oxide system: JP-A-57-95603]
No. Publication, ((NiXMgyZnz)Mn204 spinel system: JP-A No. 57-887o1), ((NjPCO
(Fe, l, Mn,)04 spinel system: JP-A-57-8
No. 8702, etc.) have been proposed, but they are still in the evaluation stage.

The present inventor also responded to the above request by filing a patent application for Mn-Nj, -Cr-Zr oxide system:
I have proposed No. 1265. This is stable Mn-Ni
It was obtained by adding ZrO2 to -Cr-based oxide spinel.

(Object of the invention) The present invention was made in view of the above problems, and it
It is an object of the present invention to provide a method for manufacturing an oxide semiconductor for a thermistor that exhibits an appropriate resistance value at temperatures of up to 500°C and can be stably used.

(Structure of the Invention) The present invention adds stabilized zirconia containing Mg as a stabilizing element to Mn-Ni-Cr-based oxide spinel,
That is, a total of 100 metal elements including manganese, nickel, chromium, zirconium, and magnesium are used.
To obtain an oxide semiconductor for thermistor containing atomic%
This is a manufacturing method that uses stabilized zirconia as a starting material.

(Example) Examples of the present invention will be described below.

Commercially available raw materials MnCO3, NiO, Cr201 and MgO, 5mail-containing zrO2 provided by the manufacturer were
n:Nj:Cr:Zr=76.0:2.0:2.0
: 20.0 IM%.

To illustrate the thermistor manufacturing process, these blended compositions are wet mixed in a ball mill, and the slurry is dried for 10 minutes.
The calcined product was calcined at 00°C, and the calcined product was again wet-pulverized and mixed using a ball mill.

After drying the obtained slurry, add and mix polyvinyl alcohol as a binder, take a predetermined amount and make a 30mmφX
Form into 15mm blocks. This molded body is 140
Calcined in air at 0°C for 2 hours.

From the block thus obtained, a wafer having a thickness of 150 to 400 μm is taken out through slicing and polishing, and platinum electrodes are provided on it by screen printing. This electrode-attached 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 figure is a diagram illustrating the resistance value change rate over time characteristics of thermistor sensors made by the method of the present invention and those made by other methods in comparison.

(1) shows the rate of change in resistance value over time at 500°C of the thermistor sensor manufactured by the above method, and (3) shows the rate of change over time of the resistance value of the thermistor sensor manufactured by the above method, and (3) shows the rate of change in resistance value over time at 500°C of the thermistor sensor manufactured by the above method, and (3) shows the rate of change over time of the resistance value of the thermistor sensor manufactured using the already proposed Mn-Ni-Cr-Zr oxide material. The rate of change in resistance value over time is shown for comparison. In (2), a sensor with the same composition ratio as the example of the present invention shown in (1) was obtained through the same manufacturing process using zirconia and magnesia as raw materials instead of stabilized zirconia. This shows the rate of change in resistance value over time. The shape of the element used in the sensor is 400 μm x 400 μm x 30
0 μm'.

The initial resistance value of the sensor at 25℃, 300℃ and 50℃
The thermistor constant B at 0°C is also shown in the table.

Table (* marks are comparative samples and are outside the scope of the claims of the present invention.) As is clear from the figure, according to the manufacturing method of the present invention, compared to samples No. 2 and No. 3, It has particularly excellent stability.

Focusing on the microstructure of the sample, the stabilized zirconia has M
It does not form a solid solution in n-Ni-Cr-based oxide spinel crystals, but exists as crystal junctions or crystal grains themselves.

On the other hand, those containing +itgo and ZrO2 at the same time,
Although ZrO2 still exists as joints or crystal grains of spinel crystals, X-ray microscopic examination of the cross section of the sintered body shows that Mg is not preferentially dissolved in ZrO2, but is present in a more or less uniformly dispersed state. It was revealed by analysis that Mn-Ni-Cr-Mg
The system oxide could not be identified.

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 creation method.

The stabilized zirconia used in this example was obtained by a coprecipitation method using oxalic acid 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 at % or less based on 100 at % of the thermistor constituent elements. Furthermore, when agate boulders were used, the amount of Si mixed was 0.1 at % or less.

=7- (Effects of the Invention) As explained above, according to the method of manufacturing an oxide semiconductor for a thermistor of the present invention, a temperature sensor with a small change in resistance value over time in the range of 200°C to 500°C can be obtained. It can be expected to contribute to fields of application that require high reliability at high temperatures, such as microwave ovens and temperature control for oil combustion.

[Brief explanation of the drawing]

The figure is a diagram illustrating the resistance value change rate over time characteristics of thermistor sensors made by the method of the present invention and those made by other methods in comparison.

Claims (1)

[Claims] For a thermistor, characterized in that magnesium-containing stabilized zirconia is used as a starting material in order to obtain an oxide semiconductor for thermistor containing a total of 100 atomic % of five types of metal elements: manganese, nickel, chromium, zirconium, and magnesium. Method for manufacturing oxide semiconductor.