Thermal expansions of Ln2Zr2O7 (Ln = La, Nd, Sm, and Gd) pyrochlore

The thermal expansions of the rare earth zirconate (Ln(2)Zr(2)O(7), Ln =La, Nd, Sm, and Gd) pyrochlore were studied by the Debye and quasi harmonic approximation combined with the first principles calculations. The difference between C-v and C-p was obtained. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to phonon excitations at relatively a low temperature. When the temperature is much higher than Debye temperature, i.e., above 600 K for Ln(2)Zr(2)O(7) compounds, the volumetric coefficient is increased linearly by increasing the temperature. The calculations are in good agreement with the experiments. (C) 2012 American Institute of Physics. Pittp://dx.doi.org/10.1063/1.4722174]