Relaxation and adiabatic calorimetry were used to measure the isobaric heat capacity of LaMnAlO hexaaluminate with a magnetoplumbite structure in the temperature range of 2–330 K. Thermodynamic functions are calculated from the fitted values of the heat capacity. The enthalpy of dissolution was measured by the drop-calorimetry into the melt, on the basis of which the enthalpy of formation of LaMnAlO from oxides and elements was calculated. The calculated Gibbs energy of the lanthanum-manganese hexaaluminate decomposition into binary oxides at high temperatures has positive values, which indicates the stability of the complex oxide. The effect of replacing magnesium with manganese on the thermodynamic stability of a hexaaluminate with a magnetoplumbite structure is assessed.
I. A. Bazhenova (Wed,) studied this question.