CALCULATION OF A PHASE-DIAGRAM FOR THE LIO0.5-ALO1.5 SYSTEM

The heats of formation at 298.15 K of Li3AlO5 and Li5AlO4 were found to be -420.22 and -561.61 kcal/mol, respectively, and the heat of disproportionate of Li3AlO3 to Li5AlO4 and LiAlO2 was found to be -0.66 kcal/mol. An equation allowing calculation of the thermodynamic parameters of γ-LiAlO2 for a wide range of temperatures was developed. The enthalpy and entropy of the high-temperature form of LiAl5O8 were obtained. Using the Redlich-Kister equations, we calculated the phase diagram for the LiO0.5-AlO1.5 system. The thermodynamics of the spinel phase and the stabilities of the α and β forms of LiAlO2 as a function of pressure are discussed. © 1979 American Chemical Society.