JPH01235201A - 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 the Invention The present invention relates to an oxide semiconductor for a thermistor having a negative temperature coefficient of resistance and which can be used as a highly responsive temperature sensor.

Conventional technology Conventionally, Mn-Co has been used as a general-purpose disk type thermistor.
-Ni-Cu oxide-based thermistor materials whose crystal structure is a spinel structure have been mainly used. The electrical characteristics of a thermistor material are generally expressed as specific resistance and thermistor constant B. The thermistor constant (hereinafter referred to as B constant) represents the temperature gradient of resistance.

Specifically, it is determined by the activation energy corresponding to the band gap of the thermistor material. Therefore, the larger the B constant, the greater the change in resistance value with respect to temperature, that is, the better the responsiveness.There is a correlation between the specific resistance and the B constant as shown in FIG.

Current general-purpose thermistor materials have a specific resistance in the area surrounded by 1 in the figure, that is, a B constant of several tens to several hundreds of kg.

Numbers of 2,600 to 5,000 are used.

In addition, as an oxide semiconductor that combines cobalt oxide and lithium, it is generally known that one of the conductive mechanisms of oxide semiconductor materials is
This is an example of the valence control theory explained as one of the ancient (71
! This is taken up by RWKY et al.

(Philips Re5eroh Report
5173 However, the study by vxawxy et al. was only at the research stage and was before the development of its use as a thermistor, and the study as a thermistor material was described by two authors (Hitachi, Ltd., Collected papers commemorating the 20th anniversary of the founding of the Central Research Institute, pages 30-45
．． There is only one (1963). According to the results of the two studies, both the resistivity and the B constant are low, and it is not suitable as a thermistor, but is described as similar to this.

Problems to be Solved by the Invention Conventionally, there have been devices designed to improve responsiveness for use in automobile water temperature gauges, iron temperature sensors, etc.
There has been a demand for a thermistor material with low resistivity (and high B constant), but the general-purpose thermistor material shown in FIG. 1 above could not satisfy this demand.

An object of the present invention is to provide a thermistor material that can satisfy this demand, that is, an oxide semiconductor for thermistor.

Means for Solving the Problems In order to achieve the above-mentioned needs, the present invention aims to solve the above-mentioned Co-Li
This problem was solved by reviewing the oxide semiconductor and making improvements. The oxide semiconductor for a thermistor of the present invention is made of a sintered mixture of metal oxides, and its metal elements include cobalt (Go)To, O~98.0 at%, and copper (Cu)0.5~4.0 at%. Atomic %, Lithium A (Li)
1.0 to 20.0 atomic % and halfnium (If) o,
It contains a total of 100 atom % of four types of es to 5.0 atom %.

Effect: With this configuration, it is possible to obtain an oxide semiconductor for a thermistor having a low resistivity in the region 2 surrounded by the solid line in FIG. 1 and a high B constant. Here, the basic composition of this semiconductor is cobalt oxide (Coo), and when dicobalt tetroxide (Cos o4') is produced,
Due to the contribution of hopping conduction, a high B constant cannot be achieved.

Example Examples of the present invention will be described below.

Commercially available raw materials, such as cobalt oxide, steel oxide, lithium oxide, and halfnium oxide, were blended to have the respective atomic % compositions as shown in the table below. Here, to illustrate the thermistor manufacturing process, these blended compositions are wet mixed in a ball mill, and the slurry is dried and then heated at 800°C.
The calcined product was wet-pulverized and mixed again in a ball mill. The slurry thus obtained is dried,
Add and mix polyvinyl alcohol as a binder,
A required amount was taken and pressure-molded into a disc shape to produce a large number of molded products, which were then fired at 1200°C to 1300°C for 2 hours in a nitrogen gas flow. Electrodes containing mug as a main component were provided on both sides of the disc-shaped sintered body thus obtained. Resistance values at 26°C and 60°C for these samples (respectively “25 and R
5°) and the specific resistance p25 at 26°C as shown below (1).
The B constant was calculated from the formula (2).

(1 = electrode area, +1 = distance between electrodes) These results are summarized in the table below.

Today's Comparative Sample As mentioned above, the region 2 surrounded by the solid line in FIG. 1 is the region of low resistivity and high B constant that is the object of the present invention. In this region, the electrical characteristics requested by the device in order to achieve high responsiveness as a sensor are replaced by the characteristics (specific resistance and B constant) of the thermistor material.

In the previous table, sample numbers 1.5, 6, 9, 10°15.
18 is not included in region 2 surrounded by this solid line. In other words, it is outside the scope of the present invention because it does not satisfy the demands of equipment manufacturers.

Although the sample used this time was one that was dry formed and then fired, a bead type element may also be used, and there are no restrictions on the element manufacturing method.

Effects of the Invention As described above, the present invention provides an oxide semiconductor for a thermistor that has a low specific resistance, a high B constant, and a negative temperature coefficient of resistance. This will improve performance and save power. Furthermore, since it is a thermistor material with unprecedented low resistivity and high B constant, it can be expected to be used in completely new applications as a sensor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a characteristic correlation diagram of a thermistor material having a negative temperature coefficient of resistance.

Claims (1)

[Claims] Consisting of a sintered mixture of metal oxides, its constituent metal elements include 71.0 to 98.0 at% cobalt and 0.6 to 98.0 at% copper.
An oxide semiconductor for a thermistor, comprising a total of 100 atom % of four types: 4.0 atom %, lithium 1.0 to 20.0 atom %, and halfnium 0.5 to 5.0 atom %.