Thermodynamic assessment of the Mn-Y-O system

The thermodynamic properties of two yttrium manganese complex oxides, h-YMnO3 and YMn2O5, were assessed. They were both treated as stoichiometric compounds. An optimized set of parameters of Gibbs energy functions is proposed. According to our calculation, in air, YMn2O5 is stable from room temperature up to 1461 K. Then it decomposes into h-YMnO3 and β-Mn3O4. h-YMnO3 is stable above 1062 K. At lower temperature, it decomposes into YMn2O5 and α-Y2O3. At 2067 K, it melts incongruently. A complete thermodynamic description of the Mn-Y-O system is proposed. The MnOx-YO1.5 phase diagram in air and three isothermal sections of the Mn-Y-O system are presented.