Patent 7767116 was granted and assigned to NGK Insulators on August, 2010 by the United States Patent and Trademark Office.
12CaO.7Al2O3 polycrystal having high conductivity is provided. The conductivity of the 12CaO.7Al2O3 polycrystal becomes 100 S/cm or more by controlling the nitrogen content in the 12CaO.7Al2O3 polycrystal within a range of 0.3 to 1.1 wt %, and that the conductivity becomes 150 S/cm or more by controlling the nitrogen content within a range of 0.5 to 0.9 wt %.