JPS63296304A - Oxide semiconductor for thermistor - Google Patents

Abstract

PURPOSE:To lower resistivity, and to increase the B constant by composing an oxide semiconductor for a thermistor of the sintered mixture of a metallic oxide and containing five kinds of cobalt, copper, lithium, zirconium and silicon at a specific rate as constituent metallic elements for the sintered mixture. CONSTITUTION:An oxide semiconductor for a thermistor consists of the sintered mixture of a metallic oxide, and five kinds of 75.3-96.5 atom % cobalt (Co), 1.0-4.5 atom % copper (Cu), 1.0-15.0 atom % lithium (Li), 1.0-12.5 atom % zirconium (Zr) and 0.0-2.0 atom % silicon (Si) (where except 0.0 atom %) are contained at 100 atom % in total as metallic elements for the sintered mixture. Consequently, the oxide semiconductor for the thermistor having low resistivity in a region 1 and a high B constant can be acquired. Cobalt oxide (CoO) is used as a basic composition in the semiconductor, and the high B constant can not be attained by the contribution of hopping conduction when tricobalt tetraoxide (Co3O4) is formed.

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, kn-Co was used as a general-purpose disk type thermistor.
-N-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, and is specifically determined by the activation energy corresponding to the band gap of the thermistor material. Therefore, the larger the B constant, the greater the resistance change with temperature.
In other words, responsiveness is improved. In addition, there is a correlation between specific resistance and B constant as shown in the figure, and current general-purpose thermistor materials are in the area surrounded by 2 in the figure, that is, the specific resistance is in the range of several 10 to several 100 Ω・1, and the B constant is 25 oO ~5000 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 valence control theory explained as one
It has been taken up by iRWKY and others ( Ph1li
ps Re5arch Report 5173 (
(1950, )) However, the study by VKRWEY et al. was only at the research stage, and it was before the development of its use as a thermistor, and the study of it as a thermistor material was based on the one described by Nihoniri ( ■Hitachi, Ltd., Collection of papers commemorating the 20th anniversary of the founding of the Central Research Institute, P30-46, 1952
year). According to the results of these two studies,
The specific resistance and B constant are both low, and it is not suitable as a thermistor, but is described as similar to thermistor.

Problems to be Solved by the Invention There has been a demand for thermistor materials with low resistivity and high B constant for use in automobile water temperature gauges, iron temperature sensors, etc., with the aim of improving responsiveness. However, the general-purpose thermistor material shown in the figure 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 provides the above-mentioned Go-Ll
This problem was solved by reviewing and improving the dispersion semiconductor. The oxide semiconductor for a thermistor of the present invention is made of a sintered mixture of metal Y oxides, and contains 75.3 to 96.51 M% of cobalt (co) as its gold component.
Copper (Cu) 1.0 to 486 atomic%,') f h (L
i)1. o~1ts, o atom%, zirconium (Zr)
1.0 to 12.6 at% and silicon (S) 0.0
-2.0 at.% (excluding 0.0 at.%) in a total of 100 at.%.

Effect: With this configuration, an oxide semiconductor for a thermistor is obtained in which the specific resistance of the region 1 surrounded by the solid line in the figure is low (and the B constant is high.Here, this semiconductor is cobal oxide) (CoO
) is the basic composition, and dicobalt tetroxide (GO504
), a high B constant cannot be achieved due to the contribution of hopping conduction.

Example An embodiment of the present invention will be described below.

Commercially available raw materials cobalt oxide, copper oxide, lithium oxide, zirconium oxide, and silicon dioxide were blended to have the respective atomic % compositions as shown in the table below. To illustrate the thermistor manufacturing process, these compounded compositions are wet mixed in a ball mill, and the slurry is dried and then aoo
The calcined product was calcined at a temperature of 'C, and the calcined product was wet-pulverized and mixed again in a ball mill. Dry the slurry thus obtained.

Add and mix polyvinyl alcohol as a binder,
A large number of molded products were prepared by taking the required material and press-molding it into a disk shape, and firing these products at 1200° C. to 1300° C. for 2 hours in a desired gas flow. Electrodes containing 5g as a main component were provided on both sides of the disk-shaped sintered body thus obtained. For these samples, the resistance values (R25 and R, respectively) at 26℃ and 60℃ were all measured, and the specific resistance ρ25 at 25℃ was calculated from the following formula (1), and the B constant was calculated using the following formula (2). Calculated from the formula.

These results are summarized in the table below.

(The American and Indian samples are for precipitation and are not claimed by the present invention.)
As described above, the region 1 surrounded by the solid line in the figure is the region of low resistivity and high B constant that is the focus 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.

Sample number 1.6, 6, 9, 10゜13.1 in my ex-husband
4.16 is not included in region 1 curved 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. Also mixed.

Zirconia boulders were used for crushing.

Effect of the invention As described above, according to the present invention, cobalt and copper.

By adding silicon to lithium and zirconium, the resistivity is even lower than that of ternary materials.

This is aimed at achieving a high B constant. Furthermore, since silicon easily vitrifies with lithium, it is necessary to supplement the amount of lithium dissolved in cobalt. Although a slight increase in the B constant is seen as an effect of adding silica, it is unclear whether the glass phase contributes.

As described above, the present invention provides an oxide semiconductor for a thermistor having a low specific resistance, a high B constant, and a negative temperature coefficient of resistance. This also allows for power savings. 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 drawings]

The figure shows the characteristic correlation 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 cobalt 75.3 to 96.5 at%, copper 1.0
~4.5 at.%, 1.0-15.0 at.% lithium, 1.0-12.5 at.% zirconium and 0.0 at.% silicon.
An oxide semiconductor for a thermistor, characterized in that it contains a total of 100 atom % of five types of 100 atom % to 2.0 atom % (excluding 0.0 atom %).