Metal oxide sintered body for thermistor, thermistor element, and method for manufacturing metal oxide sintered body for thermistor

Abstract

To suppress resistance value changes during formic acid reflow mounting by employing a protective layer other than a Y2O3 layer in a metal oxide sintered body for thermistors, thermistor elements, and a method for manufacturing the metal oxide sintered body for thermistors, thereby minimizing resistance value changes due to reduction even at high temperatures.SOLUTION: A metal oxide sintered body 1 for thermistors has the composition given by the general formula (1-z)(Ma1-yMby)(Cr1-xMnx)O3+zY2O3 (where 0.0≤x≤1.0, 0.0<y<0.5, and 0<z≤0.8); and Ma denotes at least one trivalent metal element having an ion radius larger than that of Y, and Mb represents at least one of Mg, Ca, Sr, and Ba). A (Ma,Y) oxide layer 3 is formed on the surface of the composite oxide sintered body portion 2.SELECTED DRAWING: Figure 1

Claims

1. A metal oxide sintered body used in a thermistor, General formula: (1-z) (Ma １－ｙ Mb ｙ ) (Cr １－ｘ Mn ｘ ) O ３ +zY ２ O ３ (wherein Ma represents at least one trivalent metal element having an ionic radius larger than that of Y, and Mb represents at least one of Mg, Ca, Sr, and Ba; 0.0≦x≦1.0, 0.0<y<0.5, 0<z≦0.8), wherein a (Ma, Y) oxide layer is formed on the surface of a complex oxide sintered body part represented by the formula:

2. The metal oxide sintered body for thermistors according to claim 1, A metal oxide sintered body for thermistors, characterized in that the (Ma, Y) oxide layer has a thickness of 3.8 μm or more.

3. 3. A thermistor element comprising: the metal oxide sintered body for thermistors according to claim 1; and a pair of electrodes formed spaced apart on the surface of the metal oxide sintered body for thermistors.

4. 3. A method for producing the metal oxide sintered body for thermistors according to claim 1 or 2, comprising: The raw material powders are mixed and fired to obtain a compound having the general formula: (1-z)(Ma １－ｙ Mb ｙ ) (Cr １－ｘ Mn ｘ ) O ３ +zY ２ O ３ (wherein Ma represents at least one trivalent metal element having an ionic radius larger than that of Y, and Mb represents at least one of Mg, Ca, Sr, and Ba; 0.0≦x≦1.0, 0.0<y<0.5, 0<z≦0.8), In the firing step, the raw material powder is a mixture of a Ma compound, an Mb compound, a Cr compound, a Mn compound, and a Y compound. ２ O ３ and Y are mixed together, pulverized, and then molded to prepare a molded body, which is then fired in the air or in an atmosphere with an oxygen partial pressure of 20% or more, and cooled to room temperature after firing, thereby forming a (Ma, Y) oxide layer on the surface of the complex oxide sintered body.

5. 5. The method for producing a metal oxide sintered body for a thermistor according to claim 4, a (Ma, Y) oxide layer formed on the surface of the complex oxide sintered body, the method for producing a metal oxide sintered body for thermistors, characterized in that in the firing step, the firing is performed in air or in an atmosphere with an oxygen partial pressure of 20% or more at a firing temperature of 1450°C or more, for a firing time of 5 hours or more, and for cooling to room temperature after firing for 6 hours or more.

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