Phase Equilibrium of the ErCl3-CdCl2-HCl-H2O System at 25 °C and Characterization of the New Compounds

The equilibrium solubility of the quaternary system ErCl3-CdCl2-HCl-H2O was determined at 25 °C and the corresponding equilibrium diagram was constructed. The quaternary system is complicated with four equilibrium solid phases CdCl2·H2O, 9CdCl2·2ErCl3·29H2O, CdCl2·7ErCl3·42H2O and ErCl3·6H2O. The two new compounds 9CdCl2·2ErCl3·29H2O and CdCl2·7ErCl3·42H2O have not yet been reported in literatures, and have been characterized by XRD, TC-DTG and fluorescence spectra. Results showed that the two compounds have fluorescence and upconversion fluorescence, and intensity increases with the ErCl3 ratio increasing in CdCl2·9CdCl2·2ErCl3·29H2O loses its crystal water in three steps at 55 to 215 °C and CdCl2·7ErCl3·42H2O loses its crystal water in one at 65 to 188 °C