Peculiar temperature-dependent fluorescence of EuCl_3 in LiCl molten salt as a result of phase changes

摘要

Fluorescence spectra were obtained in situ as a function of temperature (ranging from room temperature to 956 K) from a melt of EuCl_3 and LiCl. Three different characteristic Eu~(2+) fluorescence bands, associated with phase changes, were observed. The critical fluorescence dependence on temperature appearing in the blue fluorescence were resulted from the radiative relaxation from 4f~65d~1 excited state to 4f~7 (~8S_(7/2)) ground state of Eu~(2+), which was reduced from Eu~(3+) of EuCl~3 at high temperature. The fluorescence studies could provide information regarding the phase changes estimated as the stable dihalide, aggregation, and precipitation states of Eu~(2+) in alkali halide not only crystallic but also fluidic melting matrix.