Patent ID: 8093791
Filing Date: 2012-01-10
Classification: C04B,H01B,H01T

Abstract:
1. A spark plug comprising: a center electrode; a substantially cylindrical insulator provided on a periphery of the center electrode; and a grounding electrode provided such that one end thereof faces the center electrode through a spark discharge gap, wherein the insulator is formed by an alumina-based sintered body which has a theoretical density ratio of 95.0% or more, which contains a rare earth element (RE) component, Si component, and a Group 2 element (2A) component containing Mg and Ba as essential components and further containing at least other one element excluding Mg and Ba in Group 2 elements in a periodic table based on the recommendation of IUPAC 1990, and in which the rare earth element (RE) is dispersed so as to satisfy the condition described below: when 7 places of measurement line, measurement length: 180 μm, are selected in the alumina-based sintered body and the rare earth element (RE) present in each of selected measurement lines is analyzed with an energy dispersion method, a total number of measurement lines in which 8 or more peaks derived from the rare earth element (RE) are observed is 4 places or more of the 7 places.