Flexure Strength and Optical Transparency of Magnesium?Aluminate Spinel (MgAlO4): Influence of Polishing and Glass Coating

Abstract : Transparent magnesium-aluminate spinel has been under investigation for numerous transparent applications across a wide-transmission spectrum, including domes and armor windows. Surface polishing is necessary to achieve a transparent product; however, previous work on the flexure strength of spinel shows very little difference between ground or polished specimens. It is desired to increase the flexure strength of spinel. Other mechanisms for strengthening spinel, such as reducing the grain size or eliminating sintering aids, are being investigated. One method that shows some promise is the application of a thin glass coating. This is shown to improve the transparency of unpolished spinel as well as provide an additional avenue for strength improvement by minimizing surface flaws. Results showing increases in strength and transparency are presented.