| 摘要 |
An object of the invention is to provide a spark plug capable of suppressing the occurrence of cracking with a grain boundary oxidized in an outer layer as the starting point under a cold and/or hot environment while decreasing temperature increase of a ground electrode. A spark plug of the invention including a center electrode and a ground electrode having a gap between the center electrode and the ground electrode in which the ground electrode has at least a core portion and an outer layer covering the core portion, and the core portion is formed from a material having higher thermal conductivity than that of the outer layer, wherein at least a portion in which thickness of the outer layer is 0.5 mm or less exists at a cross-section perpendicular to a direction in which the ground electrode is extended, and the composition of the electrode material forming the outer layer is as follows: Ni is 96 mass% or more, total of at least one kind selected from a group consisting of Y and rare earth elements is 0.05 mass% or more, Al is 0.5 mass% or less, and Si is 0.5 mass% or more and 1.5 mass% or less (here, the total of Ni, Y, rare earth elements, Al, Si does not exceed 100 mass%). |
