| 摘要 |
PROBLEM TO BE SOLVED: To improve a sliding characteristic of a fixing valve element and a movable valve element, sufficiently improve durability without changing a device even if it is used for a long time, and reduce costs by forming at least one of sliding contact surface in the fixing valve element and the movable valve element by a ceramic body including compound oxide particle expressed in a specified chemical formula. SOLUTION: At least one of sliding contact surface in a fixing valve element and a movable valve element is formed of ceramic body including compound oxide particle of spinel type structure expressed in a formula of AB2O4 as metallic elements A and B. Aluminum is more preferably in the metallic element B, The metallic element A is one kind element selected from magnesium, cobalt, nickel, copper, manganese, and iron. Ceramics as a parent phase is more preferablyα-alumina (α-Al2O3), 5 to 100 weight% of compound oxide particle with respect to 100 weight% of alumina is blended as a blending rate.
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