Lattice strain and dislocations in polished surfaces on sapphire

Polishing of ceramics, surface defects and strain are introduced that influence the mechanical properties in the final products. In this study, the sapphire surfaces with a-plane and c-plane were polished using several kinds of diamond slurry, and the introduced damaged zones were investigated using transmission electron microscopy (TEM), high-resolution TEM, and TEM-CBED (convergent beam electron diffraction). It was found that the types of slip systems and strain distribution were different between the a-plane-polished and the c-plane-polished specimens. That is, the basal slip and the prism slip were mainly activated in the c- and a-plane-polished specimens to form the different damaged zones. This difference was probably due to the difference in the direction and angle from the slip plane and applied shear stress during the polishing. On the basis of these observations, the types of introduced dislocations and distribution of strain were discussed to clarify the mechanism of polishing.