Compressive stress, sapphire

The Raman scattering in Si nanociystals non-unifonnly distributed in Si02 (fused quartz) and AI2O3 (sapphire) matrices was studied. The mean diameter of the nanocrystals in Si02 is detemiined that is consistent with electron microscopy data. In case of nanocrystals embedded in AI2O3 Raman shifts indicate existence of a compressive stress that suppress Si nanociystal photoluminescence. 

The plastic deformation of the sapphire occurred due to basal and prismatic slip during loading above T. Basal slip was found in A- and B-oriented specimens and prismatic slip in C-oriented specimens. The resolved stresses at yield (according to the author) are comparable to those measured by other researchers under compression in the appropriate slip system. 

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