Wide-range thermistor material and method for producing it

A wide-range thermistor material comprising:

• a range of temperature-dependant resistance change of 10 to 10.sup.4 ;
• and
• a matrix formed of an electrically-insulating ceramic;
• and
• second phase materials discontinuously dispersed in said matrix, and formed of a semiconductive or conductive substance having a rate of temperature-dependant resistance change of 100 times or more.

A method for producing a wide-range thermistor materials,

• said wide-range thermistor material comprising:
• a rate of temperature-dependant resistance change of 10 to 10.sup.4 ;
• a matrix formed of an electrically-insulating ceramic;
• and
• second phase materials discontinuously dispersed in said matrix, and formed of a semiconductive or conductive substance having a large rate of temperature-dependent resistance change;
• wherein said method comprises:
• a step of mixing an insulating ceramic powder and a sintering aid to prepare a matrix powder;
• a step of granulating the matrix powder into particles having a particle size of from 5 to 500 .mu.m;
• a step of mixing a semiconductive or conductive, second phase material powder and at least one semiconductive or conductive additive selected from nitrides, borides, silicides, sulfides and carbides of elements of Group IVa, Group Va, Group VIa, and Group IIb to Group Vb, and their composite compounds to prepare a composite powder;
• a step of mixing the granulated matrix powder and the composite powder, or surrounding the particles of the granulated matrix powder with the composite powder to prepare a mixture powder;
• and
• a step of shaping and sintering the mixture powder to form a sintered body thereof.

A method for producing a wide-range thermistor material,

• said wide-range thermistor material comprising:
• a rate of temperature-dependant resistance change of 10 to 10.sup.4 ;
• a matrix formed of an electrically-insulating ceramic;
• and
• second phase materials discontinuously dispersed in said matrix, and formed of a semiconductive or conductive substance having a large rate of temperature-dependent resistance change;
• wherein said method comprises:
• a step of mixing a semiconductive or conductive, second phase material powder and an insulating ceramic matrix powder optionally along with a sintering aid to prepare a composite powder in which the second phase powder has a particle size not larger than 1/2 of that of the matrix powder;
• and
• a step of diepressing and sintering the composite powder, in which the sintering step may optionally includes heat treatment for growing crystal grains of the matrix.