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 gamma- MgAlON spinel solution was successfully described by the extension of gamma- MgAl 2 O 4 spinel in MgO-Al2O3 system and gamma- 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.