Critical assessment and thermodynamic modeling of the Al-Mn-O system

Phase relations in the Al2O3-MnOx system have been investigated in the range of 1373-2053 K using XRD, SEM/EDX, and DTA. It has been observed that Al2MnO4 melts by peritectic reaction at 2000 K. The heat capacity measurements of the stoichiometric Al2MnO4 compound has been carried out in the temperature range of 250-873 K using DSC. A new thermodynamic description of the Al-Mn-O system has been derived within the CALPHAD approach using own experimental data on the phase equilibria and available experimental data on the degree of inversion of stoichiometric spinel Al2MnO4, standard entropy, and its Gibbs energy of formation from oxides. Solid phases have been modelled using the compound energy formalism. Liquid phase has been described by the two-sublattice model for partially ionic liquid. Thermodynamic parameters have been evaluated to describe experimental data in the whole compositional range of the system under reducing conditions and in air. (C) 2021 Elsevier B.V. All rights reserved.