Critical evaluation and thermodynamic modeling of the AlN-Al2O3 and the AlN-Al2O3-MgO systems and applications to AlN and MgAlON sintering process

Thermodynamic modeling of the AlN-Al₂O₃ system and AlN-Al₂O₃-MgO system was carried out in the present study based on the critical evaluation of all available data. The γ-MgAlON spinel solution was successfully described by the extension of γ-MgAl₂O₄ spinel in MgO-Al₂O₃ system and γ-AlON spinel in AlN-Al₂O₃ system. The liquid solution in the AlN-Al₂O₃-MgO system was also well described by the reciprocal liquid solution (Al,Mg//O,N) using Modified Quasi-chemical Model with Quadruplet Approximation (MQMQA). The liquidus projection of the AlN-Al₂O₃-MgO system was predicted for the first time. The present thermodynamic modeling results can be used for calculations of any chemical reactions and phase diagrams within the entire AlN-Al₂O₃-MgO system. As applications of the present thermodynamic database, the phase evolutions in the sintering processes for AlN ceramics with MgO additive and transparent MgAlON ceramics were simulated to give the guidance for the sintering processes.