Low-temperature phase transition phenomena for bismuth-substituted La2Mo2O9

Phase relation and transition behavior of the heat-treated La2–xBixMo2O9 (x = 0.06) have been investigated by means of thermal analyses. When the sample is annealed below 460 °C, a small endothermic signal appears with the onset temperature of 470 °C, which is ascribed to formation of the β-related stable phase (β′-phase) during annealing. The enthalpy change at β′–β transition has been determined to be 1.81 kJ mol− 1, which is smaller than that of α–β transition. The β → β′ phase change process has been expressed by Avramiʹs equation with thermally activated rate constant.