JPS63308302A - Oxide semiconductor for thermistor - Google Patents

Abstract

PURPOSE:To obtain negative resistance temperature coefficient having lower specific resistance and higher B constant than those of a 4-ingredient material by adding specific amounts of cobalt, copper, lithium, nickel and further zirconium. CONSTITUTION:A sintered mixture of metal oxide is provided by containing as metal elements 68.0-94.5 atomic % of cobalt Co, 0.4-5.5 atomic % of copper Cu, 2.5-22.0 atomic % of lithium Li, 0.5-6.0 atomic % of nickel Ni and 0.5-4.0 atomic % of zirconium Zr, totally 100 atomic %. Thus, a thermistor material which has low specific resistance and high B constant for the purpose of improving its responsiveness as a water temperature meter for an automobile or a temperature sensor for an iron is obtained.

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-Go 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, and is specifically determined by the activation energy corresponding to the band gap of the thermistor material. Therefore B
The larger the constant, the larger the change in resistance value with respect to temperature, that is, the better the response. In addition, there is a correlation between specific resistance and B constant as shown in the figure, and current general-purpose thermistor materials have a specific resistance in the area surrounded by 2 in the figure, that is, a specific resistance of several 10 to several 10
0 and a B constant of 2,500 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 a practical example of valence control theory explained as one
Covered by RWEY et al.

(Philips Re5erch Report
5j73 However, the study by vEnwxy et al. was only at the academic stage, and was before the development of its use as a thermistor, and the study on its use as a thermistor material was based on the one described by Nimoto Irio (■Hitachi, Ltd. Collected papers commemorating the 20th anniversary of the founding of the Central Research Institute, P30~
46, 1960). According to the results of these 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 has been a demand for thermistor materials with low resistivity and high B constant for the purpose of improving responsiveness, such as for use in water temperature gauges in automobiles or temperature sensors in irons. However, the general-purpose thermistor material shown in the figure above could not meet 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 Co-Li
This problem was solved by reviewing the oxide semiconductor and making improvements. The oxide semiconductor for thermistor of the present invention is made of a sintered mixture of metal oxides, and the metal elements thereof include cobalt (Co) of 68.0 to 94.5 atomic % and copper (Cu) of 0.4 to 5.5 atomic %. Atomic %, lithium (Li)2.
s ~ 22.0 at%, Nickel # (Ni) 0.5 ~ 6.0
and zirconium (Zr)O,S~4.0 at% 5
It contains 100 atomic percent of seeds in total.

Effect: With this configuration, an oxide semiconductor for a thermistor is obtained in which the region 1 surrounded by the solid line in the figure has a low resistivity and a high B constant. Here, this semiconductor is cobalt oxide (Coo
) is the basic composition, and tricobalt tetroxide (Co, 0
4), a high B constant cannot be achieved due to the contribution of hopping conduction.

Example Examples of the present invention will be described below.

Commercially available raw materials cobalt oxide, copper oxide, lithium oxide, nickel oxide, and zirconia were blended to have the respective atomic % compositions as shown in the table below. To illustrate the thermistor manufacturing process, these blended compositions 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 thus obtained is dried, polyvinyl alcohol is added and mixed as a binder, the required amount is taken and pressure molded into a disk shape to make a number of molded products, and these are heated at 1200°C to 1300'C in a nitrogen gas flow for 2 hours. Baked for an hour. Mug was applied to both sides of the disk-shaped sintered body thus obtained.
An electrode whose main component is About these samples2
The resistance values (R25 and R58, respectively) at 6℃ and 60℃ were measured, and the specific resistance ρ25 at 26℃ was calculated as follows (1
), and the B constant was calculated from the following equation (2).

25 25 d--” (1) (S=electrode area, d=interelectrode distance) These results are summarized in the table below.

(Hereinafter referred to as Shimokin White) (Note) * is a comparative example and is outside the scope of the claims.

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 object of the present invention. In this region, the electrical characteristics required by the device to achieve high responsiveness as a sensor are replaced by the characteristics (specific resistance and B constant) of the thermistor material.

In the chart, sample numbers 1.5, 6, 8, 9, 12゜1
3, f5. j7 is not included in region 1 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. In addition, sample number 16 has already been proposed by the present inventors.

Although the sample used this time was one that was dry formed and then fired, a peed 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 zirconium to lithium and nickel, the aim is to achieve lower resistivity and higher B constant than the four-component material, but the addition of zirconia improves the sinterability of the ceramic and its resistance when manufactured in large quantities. The coefficient of variation of the value has become smaller. Although no remarkable effects were observed in terms of low resistivity and high B constant, it is thought to be almost equivalent to the four-component system of Co, Cu, Li, and Ni, and the above-mentioned effects were confirmed.

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 also brings about effects such as power saving. Furthermore, since it is a thermistor material with unprecedented low resistivity and high B constant, it is expected that it will be used in completely new applications as a sensor.

[Brief explanation of drawings]

The scale diagram is a diagram showing a characteristic correlation diagram of a thermistor material having a negative temperature coefficient of resistance. 1...Characteristic range of the present invention with low resistivity and high B constant.

Claims (1)

[Claims] Consisting of a sintered mixture of metal oxides, its constituent metal elements include 68.0 to 94.5 atomic percent cobalt and 0.4 atomic percent copper.
~5.5 at%, lithium 2.5~22.0 at%, nickel 0.6~6.0 at%, and zirconium 0.5~
An oxide semiconductor for a thermistor, comprising a total of 100 atom % of five types of 4.0 atom %.