SPARK PLUG

摘要

To provide a spark plug which exhibits excellent withstand voltage characteristics at high temperature and high resistance to an acidic atmosphere and a basic atmosphere. The spark plug of the invention has an insulator containing an Al component, in terms of oxides, 89 mass% or more and a Ti component, in terms of oxides, more than 0 mass% and 0.2 mass% or less, characterized in that the insulator is formed of an alumina-based sintered material which contains, in a grain boundary phase present between alumina crystal grains, a first crystal phase containing at least one species selected from among an La component, an Nd component, a Pr component, a Y component, an Er component, a Yb component, and an Lu component, and a second crystal phase containing at least one species of Group 2 element components, the Group included in the periodic table defined by Recommendations 1990, IUPAC, an Al component, and an Si component.