| 摘要 |
PROBLEM TO BE SOLVED: To provide a ceramic heater which can hold initial performances for a long period and has high reliability. SOLUTION: A structure wherein a ceramic resistor 12 is buried in an insulator 11 made of ceramic constituted mainly of silicon nitride is adopted for a ceramic heater used for a glow plug. The ceramic resistor 12 is constituted of conductive ceramic particles such as WC, secondary ceramic particles produced in burning, such asβ-sialon, and a boundary particle phase containing 2E2 O3 .Si2-x Alx N2-x O1+x wherein E denotes a rare-earth element and 0<x<2. Since the secondary ceramic particles exist in the ceramic resistor 12, the thermal expansion coefficients of the ceramic insulator 11 and the ceramic resistor 12 become close to each other and thereby a disconnection due to a thermal expansion difference is prevented. Since the secondary ceramic particles and the boundary particle phase meeting the above-mentioned chemical formula are present among the conductive ceramic particles, besides, an electrolysis of substances among the conductive ceramic particles is suppressed by a potential difference and a rise of a resistance value is prevented.
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