Sintering chemical reactions to increase thermal conductivity of aluminium nitride

Abstract

Chemical reactions to increase thermal conductivity by decreasing oxygen contents during AlN sintering with an Y2O3 additive in a reducing nitrogen atmosphere with carbon were investigated. They were: Al2O3 + N2 + 3CO ⇋ 2AlN + 3CO2, Al2Y4O9 + N2 + 3CO ⇋ 2AlN + 2Y2O3 + 3CO2 and Y2O3 + N2 + 3CO ⇋ 2YN + 3CO2. Some of the CO2 gas reduced to CO gas in the presence of carbon by a chemical reaction: CO2 + C ⇋ 2CO. These reactions were confirmed by examining oxygen contents, the grain boundary phases of the sintered AlN, and the trapped CO and CO2 gases in the sintered bodies. These reducing reactions proceed with increasing sintering temperature and periods, and hence the thermal conductivity is increased. © 1991 Chapman & Hall.