Translucent and fully transparent polycrystalline aluminum oxynitride (AlON) ceramics have been produced by reaction sintering, hot-pressing, and conventional sintering. Initial work to produce AlON via transient liquid phase sintering resulted in a material with significant porosity. Attempts to promote densification by altering the sintering time and temperature further increased porosity. No vapor phase had been previously reported in the literature, however, so we therefore undertook a new investigation into the AlN-Al_2O_3 pseudo binary phase diagram, the results of which suggested the presence of a stable vapor phase in 0.1 MPa (1 atm) nitrogen. This paper describes the effect of increasing nitrogen gas pressure on the stability of AlON. Our results show stabilization in composition of AlON as measured by reduced lattice parameter and reduced weight loss as the pressure is increased.
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