| 摘要 |
A spark plug insulator having a sintered body including aluminum nitride ceramic powder in an amount in the range 60% to approximately 98% by weight of the sintered body and a sintering additive, the sintering additive is selected from yttrium oxide (Y2 O3), calcium oxide (CaO), barium oxide (BaO), calcium carbide (CaC2), neodymium oxide (Nd2 O3) and scandium oxide (SC2 O3). A layer of pyrolytic boron nitride uniformly is deposited on an entire surface of the sintered body, the thickness of the pyrolytic boron nitride layer ranging from 10 .mu.m to 100 .mu.m The pyrolytic boron nitride is deposited on the sintered boy by placing the sintered body in a carbon furnace in which boron chloride (BC1 3) and ammonia gas (NH3) chemically react at a reaction temperature of 1900.degree.C under 10 -2 to approximately 10 -3 Torr so as to form a pyrolytic boron nitride which is deposited on the entire surface of the sintered body to provide a pyrolytic boron nitride layer placed at a rate of 20 to approximately 30 .mu.m per hour. |
