XAFS analysis of molten rare-earth-alkali metal fluoride systems

X-ray absorption fine structure (XAFS) measurements on rare-earth-alkali metal fluoride systems (0.2 LnF3–0.8 MF: Ln = La, Ce, Nd, Sm; M = Li, Na, K) have been carried out at 300 and 1173 K. The local structures around rare-earth-ions in both the solid and liquid phases were evaluated by the curve-fitting analysis, involving anharmonic oscillation effects at the higher temperature. This study revealed that the nearest-neighbour Ln3+–F− distance and the corresponding coordination number of F− around Ln3+ in the molten state mainly depend on the lanthanide species rather than the size of the alkali metal ion.