Abstract: he thermodynamic properties of Mg-Al-O-N system were evaluated and the phase stability diagram of MgAlON was
established. Based on the thermodynamic analysis, MgAlON with different compositions was synthesized. The microstructures, crystalline
characteristics, mechanical properties and oxidation resistance of the synthesized materials were experimentally measured and discussed.
A standard diffraction file of MgAlON was suggested. X-ray diffraction and TEM analysis show that there is no other phase than MgAlON
detected. HREM analysis of MgAlON indicates that there is no glass phase existed at the grain boundaries, the grains are bounded directly.
Three-point bending strength of MgAlON keeps very high until 1723K. Oxidation experiments of MgAlON show that the activation energies of oxidation during the chemical
reaction rate controlling stage and that during the diffusion controlling stage are 260 kJ/mole and 573 kJ/mole, respectively.

Key words: MgAlON, synthesis, thermodynamics, properties