Raman spectroscopy was used to analyse the crystal structures of hot isostatically pressed specimens which contained 0.5mol%Y2O3 and 0.5mol%Nd2O3, plus 1wt% of Si3N4 whiskers. This technique revealed the presence of a 514 to 520/cm peak that indicated whether stacking faults were present. In gas-pressure hot-pressed material, stacking faults occurred in the ß-phase. It was found that structural defects in the grains caused phonon-impurity scattering and resulted in a decrease in thermal conductivity. It was concluded that structural defects in the grains would have to be eliminated in order to optimise the thermal conductivity.

Raman Spectroscopic Analysis of Structural Defects in Hot Isostatically Pressed Silicon Nitride. Y.Akimune, F.Munakata, K.Matsuo, N.Hirosaki, Y.Okamoto, K.Misono: Journal of the Ceramic Society of Japan, 1999, 107[4], 339-42