Patent ID: 8866370

Claim:
A spark plug comprising: a center electrode and a ground electrode having a gap between the center electrode and the ground electrode, wherein the ground electrode has at least a core portion and an outer layer covering the core portion, the core portion is formed from a material having higher thermal conductivity than that of the outer layer, 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 composition of 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 from 0.5 mass % to 1.5 mass % (here, total of Ni, Y, rare earth elements, Al, Si does not exceed 100 mass %), wherein Mn is 0.05 mass % or more, total of at least one kind selected from an element group A consisting of Ti, V, and Nb is 0.01 mass % or more, and ratio (a/b) between the content (b) of Mn and total content (a) of the element group A is from 0.02 to 0.40 in the composition of the electrode material.