| 摘要 |
A spark plug includes a center electrode, an insulator provided outside the center electrode, a metallic shell provided outside the insulator, a ground electrode disposed to oppose the center electrode, and a spark discharge portion fixed on at least one of the center electrode and the ground electrode for defining a spark discharge gap. The spark discharge portion is formed from an alloy containing Ir as a main component, Rh in an amount of 0.2 to 10 wt. %, and Pt in an amount not greater than 10 wt. %. The ratio WPt/WRh of the Pt content to the Rh content falls within the range of 0.1-1.5.
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