Simultaneous determination of X-ray Debye temperature and Grüneisen constant for actinide dioxides : PuO2 and ThO2

Abstract The lattice vibrations of PuO 2 and ThO 2 were examined between room temperature and 1274 K using a high temperature X-ray diffractometer. The temperature factors for the metal atom, B Pu and B Th in the dioxides were evaluated by the Rietveld analysis. Debye temperature was calculated using the temperature factor. It was confirmed that the Debye temperature decreased with increasing temperature. From the temperature dependence of the Debye temperature, the Gruneisen constants were evaluated to be 1.62 for PuO 2 and 1.51 for ThO 2 . The Debye temperatures modified for the thermal expansion of PuO 2 and ThO 2 were 429 and 463 K, respectively.