Phase Relations and Reaction Sintering of Transparent Cubic Aluminum Oxynitride Spinel (ALON)

A new isobaric, condensed phase diagram in the region of stability of cubic aluminum oxynitride spinel (ALON) along the pseudobinary AI₂O₃-AIN composition join is presented, deduced primarily from various analytical measurements and microstructural observations. It is shown that cubic aluminum oxynitride spinel melts incongruently at ≊2050°C and is compositionally centered at ≊35.7 mol% AIN, which is equivalent to the following stoichiometric composition: AI₂₃O₂₇N₅ or 5AIN·9AI₂O₃. Single-phase ALON material sintered to nearly full density exhibits transparency in visible light.