Abstract: A ceramic heater comprises a heat generator made of a conductive ceramic sintered body, a supporter made of an insulating ceramic sintered body for supporting the heat generator, and a metallic wire for supplying an electric current from an electrode to the heat generator. The heat generator is integrally covered with an unporous covering layer made of an insulating ceramic sintered body. The covering layer prevents the heat generator from being directly exposed to oil and water. The covering layer is made of, for example Si.sub.3 N.sub.4 or glass containing SiO.sub.2 as a main constituent into a thickness of not more than 1mm.

Abstract: A ceramic heater device has a housing section and a heating section. The heating section includes a sintered ceramic insulator attached to a metal housing and a U-shaped sintered ceramic heater body fixed to the insulator, so that the heater body is supported by the housing section by means of the insulator in order to avoid a direct connection between the metal housing and the heater body. As a result, heat generated at the heater body may not be transferred to the metal housing, and thereby the heat can be effectively used to ignite a mixture of air and fuel in an engine and a rigid and stable support of the heater body to the metal housing can be obtained.

Abstract: A ceramic heater comprising a supporting member made of an electrically insulating ceramic and a heater element made of a ceramic having excellent oxidization resistance, thermal shock resistance and high bending strength at a high temperature is disclosed. The heater element is formed by sintering a mixture composed of MoSi.sub.2 and 10 to 70 mol % of Si.sub.3 N.sub.4. By adding 3 to 10 mol % of at least one material selected from the group consisting of Al.sub.2 O.sub.3, a mixture of Al.sub.2 O.sub.3 and MgO and MgAl.sub.2 O.sub.4 to the above mixture, a heater element having a sufficient sintering degree can be obtained even by atmospheric sintering.