Subsolidus phase diagrams of the Yb-Mn-O and Lu-Mn-O systems

Subsolidus phase diagrams for the Ln-Mn-O (Ln = Yb, Lu) systems in air were constructed over the temperature range 800-1400 degreesC based on an XRD a nalysis of homogeneous and heterogeneous phases of compositions R = N-Mn/(N -Mn + N-Ln) = (1/5), (1/2)(LnMnO(3)), (3/5), (2/3)(LnMn(2)O(5)) (4/5). The boundaries of seven phase regions [Ln(2)O(3) + LnMnO(3) (1), LnMnO(3) + gam ma -MsO4 (2), LnMnO(3) + beta -Mn3O4 (3), LnMn(2)O(3) + beta -Mn3O4 (4), Ln Mn(2)O(5) + alpha -Mn2O3 (5). LnMnO(3) + LnMn(2)O(5) (6), and a region with nonequilibrium phase composition (7)] are established. The temperatures of the monovariant equilibria LnMn(2)O(5) = LnMnO(3) + (1/3)Mn3O4 + (1/3)O-2 were determined: 1060 degreesC for Ln = Yb and 995 degreesC for Ln = Lu. No effect of the cooling mode on the phase composition of the systems was dis covered. Based on the fact that the parameters of the unit cells of the LnM nO(3) and LnMn(2)O(5) double oxides are independent of the chemical composi tion R, synthesis temperature, it was assumed that the systems under study were stoichiometric in the metals and oxygen.