Deformation under nanoindents in sapphire, spinel and magnesia examined using transmission electron microscopy

Abstract Cross-sections through nanoindentions in the (001) surface of sapphire, spinel and magnesia have been examined in the transmission electron microscope. Electron-transparent sections were prepared using a focused ion beam microscope. All three recognized high-temperature slip systems were observed in sapphire, while spinel deformed in slip bands on the {111} planes. Evidence was obtained for slip on {110} planes in magnesia and the possibility that slip also occurs on {100} planes is discussed as an explanation of its high ratio of hardness to yield stress.