JPH01235202A - Oxide semiconductor for thermistor - Google Patents

Abstract

PURPOSE:To obtain oxide semiconductor for thermistor having low resistivity and high B constants, by baking mixture of metal oxide whose constituting metal elements are specified. CONSTITUTION:The title semiconductor is composed of sintered mixture of metal oxide, and contains the following four kind of constituting metal elements whose sum is 100atom%; cobalt 75.5-98.0atom%, copper 0.5-7.0atom%, lithium 1.0-15.0atom% and titanium 0.5-2.5atom%. Thus oxide semiconductor for thermistor having low resistivity, high B constants and negative temperature coefficient of resistance is obtained, and high response to temperature as a sensor can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention can be used as a highly responsive temperature sensor.
The present invention relates to an oxide semiconductor for a thermistor having a negative temperature coefficient of resistance.

Conventional technology Conventionally, Mn-Co has been used as a general-purpose disk type thermistor.
-Ni-Cu oxide-based thermistor materials, and those whose crystal structure has 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 the 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 higher the temperature The change in resistance value is large, that is, the responsiveness is improved. In addition, there is a correlation between specific resistance and B constant as shown in Figure 1, and current general-purpose thermistor materials have specific resistances in the area surrounded by 1 in the figure, that is, in the range of several tens to hundreds of Ω, (7j, Those with a B constant of 2,500 to 6,000 IC are used.

In addition, as an oxide semiconductor that combines cobalt oxide and lithium, it is an example of the valence control theory that is generally explained as one of the conductive mechanisms of oxide semiconductor materials.
It was picked up and published by WIEY et al. (Philip
! ! Re! ! 6r6h Report 5173 However, the study by VIRWICY et al. was only at the research stage, and was before the development of use as a thermistor, and the study as a thermistor material was described in two books (Hitachi, Ltd.). Seisakusho, Collection of papers commemorating the 20th anniversary of the founding of the Central Research Institute, pages 30-46, 1960)
There is only. According to the results of the two studies, both the specific resistance 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 specific resistance (and high B constant), but the general-purpose thermistor material shown in FIG. 1 above could not satisfy these demands.

The 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-L
This problem was solved by reviewing the i-based 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 the metal elements thereof include cobalt (Co) of 75.5 to 98.0 at%,
Copper (Cu) 0.5 to 5.0 atomic%, lithium (Li)
1. O~16.0 at% and titanium:/(Ti) 0.
It contains 2 to 2.5 atom % of four types in total of 100 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 the nickel semiconductor is cobal oxide (Coo), and when dicobal tetroxide (Co, 04) is produced, a high B constant is achieved due to the contribution of hopping conduction. I can't.

Example Examples of the present invention will be described below.

Commercially available raw materials, such as cobalt oxide, copper oxide, lithium oxide, and titanium oxide, were blended to have the respective atomic % compositions as shown in the table below.

Here, to illustrate the thermistor manufacturing process, these composition parts were wet mixed in a ball mill, the slurry was dried and calcined at a temperature of 800'C, and the calcined product was wet-pulverized and mixed again in a ball mill.

The slurry obtained in this way is dried, polyvinyl alcohol is added and mixed as a binder, the required amount is taken and pressure molded into disk shapes to make a large number of molded products, and these are heated under nitrogen gas
It was baked at 0-1200°C to 1300°C for 2 hours.

Electrodes containing Mgt'' as a main component were provided on both sides of the disk-shaped sintered body O thus obtained.

The resistance values (0R25 and R50, respectively) at 26°C and 6o''C were measured for these samples, and the specific resistance ρ25 at 26°C was calculated from the following equation (1) and the B constant gold (2
) Calculated from the formula.

ρ25=R25×- (1) (S=electrode area, d-interelectrode distance) (2) These results are summarized in the table below.

(The * mark is a sample for comparison) 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.

For my ex-husband, sample numbers 1, 5, 6, 9, 10°14.
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 75.5 to 98.0 atomic percent cobalt and 0.5 to 98.0 atomic percent copper.
A total of 100 at% of four types: 7.0 at%, 1.0 to 15.0 at% of lithium, and 0.5 to 2.5 at% of titanium.
An oxide semiconductor for a thermistor comprising: