DEFECT FORMATION IN BETA-AL2TIO5 AND ITS INFLUENCE ON STRUCTURE STABILITY

Atomistic simulation calculations are used to predict the formation enthalpies of Schottky, Frenkel and anti-site defects. The latter are so easily formed that the beta-Al2TiO5 structure is predicted to be essentially cation disordered, in agreement with experimental results. Conversely, conventional Schottky and Frenkel disorder is negligible and clusters of vacancy defects are strongly bound. This leads to a significant barrier for dissociation to Al2O3 and TiO2 despite the positive calculated and observed formation enthalpy of Al2TiO5. The solution mechanisms of MgO and excess TiO2 in beta-Al2TiO5 are discussed.