Patent ID: 8614542

Claim:
A ceramic material for an insulator of a spark plug comprising, in weight percent (wt %) of said ceramic material, aluminum oxide (Al 2 O 3 ) in an amount of 98.00 wt % to 99.50 wt %; at least one oxide of a Group 2 alkaline earth metal (Group 2 oxide) in an amount of 0.16 wt % to 0.70 wt %; said at least one Group 2 oxide including at least one of calcium oxide (CaO), magnesium oxide (MgO), beryllium oxide (BeO), strontium oxide (SrO), barium oxide (BaO), and radium oxide (RaO); silicon dioxide (SiO 2 ) in an amount of 0.25 wt % to 0.75 wt %; at least one oxide of a Group 4 transitional metal (Group 4 oxide) in an amount of 0.01 wt % to 0.16 wt %, said at least one Group 4 oxide including at least one of zirconium oxide (ZrO 2 ), titanium dioxide (TiO 2 ), hafnium oxide (HfO 2 ), and rutherfordium oxide (RfO 2 ); and at least one oxide of a Group 1 alkali metal (Group 1 oxide) in an amount less than 0.0060 wt %; said at least one Group 1 oxide including at least one of potassium oxide (K 2 O), sodium oxide (Na 2 O), lithium oxide (Li 2 ), rubidium oxide (Rb 2 O), cesium oxide (Cs 2 O), and francium oxide (Fr 2 O).