Evolution of phase equilibrium states in the Tm-Mn-O system at thermal dissociation of the TmMn2O5 compound
The phase equilibria in the Tm-Mn-O system during step-by-step removal of oxygen from the TmMn2O5 static compound have been investigated using the static method (vacuum circulation setup, T = 973–1190 K) with X-ray powder diffraction analysis of quenched solid phases. It is found that dissociation of TmMn2O5 proceeds in three stages. The temperature dependences of the equilibrium oxygen pressure for the found phase equilibria have been experimentally determined. The changes in the standard thermodynamic functions of the reactions of dissociation and formation of TmMn2O5 and TmMnO3 from the corresponding elements are calculated.