Phase transformations of rare earth sesquioxides La2O3, Nd2O3, Pr2O3 and Y2O3

The C form of La2O3 has been prepared and its transformation to the A form is found to take place at ∼590°C. The C→A transformation of Nd2O3 takes place at 550°C. The temperatures as well as the energies of activation of the phase transformations of the rare earth sesquioxides vary with the size of the cation. Y2O3 undergoes a reversible phase transformation in the temperature range 400–900°C. The phase transformation of La2O3, Nd2O3 and Pr2O3 have been followed by electrical conductivity measurements. Presence of water vapour lowers the activation energy for the conduction process as well as the temperature of transformation.