Solubilities were studied for the ternary systems of CsBr−LaBr 3 −H 2 O and CsBr−CeBr 3 −H 2 O at 298.15 K using the isothermal solubility method; the corresponding phase diagrams were constructed. The solid phases were determined by the Schreinemakers wet residues technique. Three solid phases of CsBr, Cs 2 LaBr 5 •10H 2 O, and LaBr 3 •7H 2 O in the system CsBr− LaBr 3 −H 2 O, and those of CsBr, Cs 2 CeBr 5 •10H 2 O, and CeBr 3 •7H 2 O in the system CsBr−CeBr 3 −H 2 O were obtained, respectively. The compounds Cs 2 LaBr 5 •10H 2 O and Cs 2 CeBr 5 •10H 2 O are incongruently soluble in water. The new solid phase compounds Cs 2 LaBr 5 •10H 2 O and Cs 2 CeBr 5 •10H 2 O were characterized by chemical analysis, X-ray diffraction and thermogravimetric/differential thermogravimetric techniques. The standard molar enthalpies of solution of Cs 2 LaBr 5 •10H 2 O and Cs 2 CeBr 5 •10H 2 O in water were measured to be (49.61 ± 0.37) kJ•mol −1 and (50.83 ± 0.46) kJ•mol −1 by microcalorimetry under the condition of infinite dilution, and their standard molar enthalpies of formation were determined as being −(4739.3 ± 1.3) kJ•mol −1 and −(4729.6 ± 1.5) kJ•mol −1 . The fluorescence excitation and emission spectra of Cs 2 CeBr 5 •10H 2 O were measured. The results show that upconversion spectra of Cs 2 CeBr 5 •10H 2 O exhibit at 524 nm and 697 nm excited at 785 nm, and the intensity of the emission spectra at 524 nm is stronger than that at 697 nm. This research can provide fundamental data for the rare earth industry and future study. The phase diagrams of the ternary systems could provide the fundamental basis and serve as a guide for the preparation of Cs 2 LaBr 5 •10H 2 O and Cs 2 CeBr 5 •10H 2 O.

The phase equilibria of the ternary system CsBr + ErBr 3 + H 2 O and the quaternary system CsBr + ErBr 3 + HBr (∼12.3 %) + H 2 O at 298.15 K were determined experimentally with the isothermal solubility method. Based on the measured solubility data, the corresponding phase diagrams were plotted. In the ternary system, three crystallization regions corresponding to CsBr, 3CsBr·2ErBr 3 ·16H 2 O, and ErBr 3 ·9H 2 O were found. Similarly, there were three crystallization regions corresponding to CsBr, 3CsBr·2ErBr 3 ·16H 2 O, and ErBr 3 · 7H 2 O in the quaternary system. The phase diagrams of the ternary and quaternary systems were compared, and it showed that (1) a new double salt 3CsBr·2ErBr 3 ·16H 2 O was formed which was incongruently soluble in the two systems; (2) the area of the crystallization region of 3CsBr·2ErBr 3 ·16H 2 O increased with the increasing concentration of HBr in the equilibrium liquid phase, and (3) ErBr 3 ·9H 2 O transformed into ErBr 3 ·7H 2 O when the HBr reached a certain amount. The new solid-phase compound 3CsBr·2ErBr 3 ·16H 2 O was characterized by chemical analysis, XRD, and TG-DTG techniques. The standard molar enthalpy of solution of 3CsBr·2ErBr 3 ·16H 2 O in water was confirmed to be −(6.69 ± 0.29) kJ·mol −1 by microcalorimetry in the limit of infinite dilution and its standard molar enthalpy of formation was determined to be −(7846.1 ± 1.2) kJ·mol −1 . The fluorescence excitation and emission spectra of 3CsBr·2ErBr 3 ·16H 2 O were measured. The results indicated that up-conversion spectra of the new solid phase compound exhibit at 470 nm and are excited at 710 nm.

No abstract