| 摘要 |
PROBLEM TO BE SOLVED: To provide a ceramic heater exhibiting excellent durability even when a high voltage is applied and a glow plug comprising that heater as a heating source. SOLUTION: The ceramic heater comprises an insulator of sintered silicon nitride, and a U-shaped heater buried in the insulator wherein the insulation resistance of the insulator, interposed between one part of the heater and the other facing part, is 400Ωor above, especially 1 kΩor above at 1400 deg.C on the transverse section at a part of highest temperature. A glow plug incorporating the ceramic heater is especially useful when a high voltage is applied, e.g. after glow. The heater is composed of a conductive component of WC, MoSi2, or TiN and an insulating component of sintered silicon nitride. Insulation resistance of the insulator can be adjusted by adding a small quantity of conductive component, e.g. MoSi2, to the insulator.
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