Thermodynamic modeling of the La–Mn–Y–Zr–O system

Based on descriptions of the previously assessed sub-systems, we present a thermodynamic description of the La–Mn–Y–Zr–O system. Ideal extrapolations from ternaries to quaternaries and to La–Mn–Y–Zr–O are proved to be quite successful. The calculated isothermal sections of pseudo-ternaries at different temperatures in air are in good agreement with available experimental data. The thermodynamics at the LaMnO3–yttria-stabilized zirconia (YSZ) interface, which is of particular importance for solid oxide fuel cell (SOFC) applications, is discussed in detail. Based on phase equilibrium calculations, we conclude that La2Zr2O7 forms at the LaMnO3–Y SZ interface due to its high chemical stability. Thermodynamically, the La2Zr2O7 formation cannot be prevented by increasing the La deficiency in La1±xMnO3±δ. Increasing the yttria content in YSZ can suppress and in the end prevent the La2Zr2O7 formation. Apart from the temperature and the oxygen partial pressure, other factors, like the phase assemblage at the interface, the La deficiency in La1±xMnO3±δ, the yttria content in YSZ and so on, also influence the amount of LaO1.5 or MnOx (from LaMnO3) dissolved in YSZ.