Y. Akimune et al., Raman spectroscopic analysis of structural defects in hot isostatically pressed silicon nitride, J CERAM S J, 107(4), 1999, pp. 339-342
Raman spectroscopy was used to analyze the crystal structure of Hot Isostat
ically Pressed silicon nitride (Si3N4 containing 0.5 mol% of Y2O3, 0.5 mol%
of Nd2O3 and 1 mass% of Si3N4 whiskers) to confirm whether microstacking f
aults occurred in the beta-phase due to structural defects in the silicon n
itride grains. With this technique, the presence or absence of a 514-520 cm
(-1) peak confirms whether or not such stacking faults have occurred. For t
he beta-phase alone of orientation-controlled silicon nitride, a large grai
n diameter and high thermal conductivity were obtained. In contrast, for ga
s-pressure hot-pressed silicon nitride, the grain diameter was smaller and
stacking faults occurred in the beta-phase, even though the heat treatment
process was performed at the same temperature. It was found that structural
defects in the crystal grains caused phonon-impurity scattering, resulting
in a decline in thermal conductivity. This indicates that structural defec
ts in the grains must be eliminated to obtain high thermal conductivity. Th
e results of this study suggest that Raman spectroscopy can be an effective
technique for conducting structural analyses to determine the presence of
such defects.