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 degrees C, a small endothermic signal appears with the onset temperature of 470 degrees C, which is ascribed to formation of the beta-related stable phase (beta'-phase) during annealing. The enthalpy change at beta'-beta transition has been determined to be 1.81 kJ mol(-1), which is smaller than that of alpha-beta transition. The beta -> beta' phase change process has been expressed by Avrami's equation with thermally activated rate constant. (C) 2014 Published by Elsevier B.V.