Ceramic heater and a process for producing the same

A process for producing a ceramic heater which comprises:

• a first step of preparing a powder mixture by mixing a powder of an electroconductive ceramic selected from at least one of nitrides of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W) and lanthanum (La), carbides of these metals and molybdenum disilicide and a powder of an insulating material selected from at least one of silicon nitride, silicon carbide and aluminum oxide (Al.sub.2 O.sub.3),
• a second step of molding the powder mixture prepared in the first step and sintering the resultant ceramic molding product to form a ceramic sintered body, and
• a third step of forming, on a portion of the surface of the ceramic sintered body formed in the second step, an electroconductive layer comprising, as the main ingredient, an electroconductive ceramic selected from at least one of nitrides of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W) and lanthanum (La), carbides of these metals and molybdenum disilicide, in which electroconductive layer, the ratio of the electroconductive ceramic ingredient is greater than the ratio of the electroconductive ceramic ingredient constituting the ceramic sintered body, and the specific resistance of the electroconductive layer is smaller than the specific resistance of the ceramic sintered body.