<title>Increase of high-temperature strength of sapphire by polishing, heat treatments, and doping</title>

Abstract

Various ways to increase the 600C strength of sapphire were explored, including heat treatments, doping and improvement of fabrication techniques. Different grinding and polishing procedures were performed on sapphire disks and compression specimens. Measured strength showed correlation with fabrication procedures, with less aggressive, multi-step processes resulting in the highest strength. Simple heat treatments in oxidizing atmosphere significantly improve both compressive and biaxial flexure strength of sapphire. MgO doping was found to be very effective in increasing the compressive strength of sapphire when combined with the heat treatment.