Thermal shock resistance of aluminium oxide single crystals with different crystallographic faces

Theoretical and experimental study is made of thermal shock resistance and fracture morphology in alumina single crystals. In the experiments, the (0 0 0 1), (1 1 2̄ 0) and (1 1̄ 0 2) faces are tested under pulse heating in plasma of varying intensity. The peak temperature on the sample surface is determined by measuring separation between fragments formed during the cooling stage of the heating–cooling cycle. Fracture patterns are found to depend on the peak temperature. The temperature threshold of fracture is theoretically and experimentally quantified for the crystal faces tested. The (1 1̄ 0 2) face in sapphire crystals is demonstrated to be most stable under thermal shock loading.