Thermistor element, thermistor element production method and thermistor temperature sensor

Abstract

A thermistor element includes a thermistor body and a reduction-resistant coating covering the thermistor body. The thermistor body contains a perovskite phase of perovskite-type crystal structure represented by the composition formula: ABO3 where A is at least one A-site element and B is at least one B-site element. The reduction-resistant coating is formed of a complex oxide containing one or more of the at least one A-site element and one or more of the at least one B-site element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a thermistor element according to one embodiment of the present invention.

FIG. 1B is a sectional view of the thermistor element according to one embodiment of the present invention.

FIG. 2 is a sectional view of a temperature sensor equipped with the thermistor element according to one embodiment of the present invention.

FIG. 3 is a scanning electron microscopic (SEM) picture showing one example of material structure of the thermistor element according to one embodiment of the present invention.

Claims

1. A thermistor element comprising: a thermistor body containing a perovskite phase of perovskite-type crystal structure represented by the composition formula: ABO3 where A is at least one A-site element and B is at least one B-site element; anda reduction-resistant coating covering the thermistor body and formed of a complex oxide containing one or more of the at least one A-site element and one or more of the at least one B-site element.

2. A thermistor element according to claim 1, wherein said one or more of the at least one A-site element includes at least either one of Sr and Y; and said one or more of the at least one B-site element includes Al.

3. A thermistor element according to claim 2, wherein said one or more of the at least one A-site element is Sr; said one or more of the at least one B-site element is Al; and the complex oxide is SrAl2O4.

4. A thermistor element according to claim 1, wherein the thermistor body further includes a metal oxide phase having lower electrical conductivity than that of the perovskite phase and represented by the composition formula: MeOx where Me is one or more of the at least one A-site element and the at least one B-site element.

5. A thermistor element according to claim 4, wherein the metal oxide phase is of the same complex oxide as that of the reduction-resistant coating.

6. A temperature sensor comprising the thermistor element according to claim 1.

7. A temperature sensor according to claim 6, further comprising a metal tube accommodating therein the thermistor element, wherein the metal tube has previously been heat-treated to form a coating film of oxide on the metal tube.

8. A method for producing the thermistor element according to claim 1, comprising: forming a green thermistor composition material into a desired shape;applying a green coating material to a surface of the green thermistor composition material; and thensintering the thermistor composition material and the coating material simultaneously in such a manner that the thermistor body and the reduction-resistant coating are produced from the sintered thermistor composition material and the sintered coating material, respectively.

9. A method according to claim 8, wherein the coating material is a slurry containing therein the complex oxide.