| 摘要 |
A corrosion-resistant silicon nitride ceramics in which an adhesion enhancing layer ( 3 ), a stress relaxing layer ( 4 ) and a crack extension preventing layer ( 5 ) are laminated in this order on a ceramic substrate ( 2 ) composed mainly of silicon nitride, and a surface corrosion-resistant layer ( 6 ) composed mainly of zirconium oxide stabilized by an element of the group 3a of the periodic table is laminated. The thermal expansion coefficient (alpha<SUB>0</SUB>) of the ceramic substrate ( 2 ), the thermal expansion coefficient (alpha<SUB>1</SUB>) of the adhesion enhancing layer ( 3 ), and the thermal expansion coefficient (alpha<SUB>2</SUB>) of the stress relaxing layer ( 4 ), the thermal expansion coefficient (alpha<SUB>3</SUB>) of the crack extension preventing layer ( 5 ), and the thermal expansion coefficient (alpha<SUB>4</SUB>) of the surface corrosion-resistant layer ( 6 ) satisfy the following relational expressions (I) to (III): <?in-line-formulae description="In-line Formulae" end="lead"?>alpha<SUB>0</SUB>≈alpha<SUB>1</SUB> (I) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>alpha<SUB>3</SUB><alpha<SUB>2</SUB> (II) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>alpha<SUB>3</SUB><alpha<SUB>4</SUB> (III) <?in-line-formulae description="In-line Formulae" end="tail"?>
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