Oxygen content in beta-Si3N4 crystal lattice

beta-Si3N4 crystals were obtained through the heat treatment of alpha-Si3N4 powder with additives, Y2O3:SiO2 = 1:2 and 2:1, and subsequent acid treatm ents that removed the secondary phases. The lattice oxygen contents of thes e crystals were determined by the hot-gas extraction method to be 0.258 +/- 0.006 and 0.158 +/- 0.003 wt% for the additive compositions of Y2O3:SiO2 = 1:2 and 2:1, respectively. The oxygen dissolved in the beta-Si3N4 crystal lattice as much as in the alpha-Si3N4 crystral lattice prepared by the chem ical vapor deposition process and in the AIN crystal lattice that exhibited high thermal conductivity.