SPARK PLUG AND METHOD FOR MANUFACTURING SPARK PLUG

摘要

Disclosed is a spark plug comprising an insulator formed of an alumina-based sintered compact, which has high processability and has been produced with high productivity, and having high withstanding voltage properties and high-temperature strength. Also disclosed is a process for producing the spark plug. A spark plug (1) comprises an insulator (3). The insulator (3) comprises a dense alumina-based sintered compact having an average crystal grain diameter D(Al) of not less than 1.50 μm. In the alumina-based sintered compact, Si, Ba and a group 2 element component containing a group 2 element other than Si and Ba and a rare earth element component are contained in such a proportion that the ratio of a content S of the Si component to the total content of the content S and a content A of the group 2 element component is not less than 0.60. In the process for producing the spark plug (1), the insulator (3) is produced through a grinding shaping step of grinding and shaping the insulator (3) before firing.