Two AlN materials with different impurity contents have been studied by TEM. Impurities are found to modify the microstructure of the material by forming polytypoid grains, precipitates of Al2O3 and FeAl2O4. The 27 R polytypoid is mostly present as a whole in one grain, but mixtures of polytypoids or compositional modulation are also found. Almina precipitates are either intragranular or at triple points. The spinel phase shows a perfect epitaxy with the polytypoid phase. Complicated arrangements of dome like defects are present in most AlN 2 H grains and are chemically induced.
No takes yet. Share an insight, caveat, or question.
Hagège et al. (1988) studied this question.