Solid–Liquid Equilibria of the Ternary System CsBr–REBr₃–H₂O (RE = La, Ce) at 298.15 K, Thermal Properties of Cs₂REBr₅·10H₂O, and Fluorescent Properties of Cs₂CeBr₅·10H₂O

Abstract

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.

(Solid + Liquid) Phase Equilibria for the Systems CsBr + EuBr3 + H2O and CsBr + EuBr3 + HBr (∼12.3%) + H2O at 298.15 K and Atmospheric Pressure and Thermodynamic and Fluorescent Properties of the New Solid-Phase Compound

“…From the comparison of the present ternary system with the reported ternary systems, ,,, the phase chemical reactions of the five systems CsBr + REBr 3 + H 2 O (RE = La, Ce, Pr, Nd, and Sm) are similar in that they all have compounds 2CsBr·REBr 3 ·10H 2 O (2:1 type). The compounds 3CsBr·2REBr 3 ·16H 2 O (3:2 type) were formed in CsBr + REBr 3 + H 2 O (RE = Er and Tm) systems, so the phase chemical reactions of the two systems are analogous.…”

“…29 The literature data seem to be distinctly overestimated. 23,30 From the comparison of the present ternary system with the reported ternary systems, 13,14,21,22 3 shows the solubility for the quaternary system of CsBr + EuBr 3 + HBr (∼12.3%) + H 2 O and the central projection data on the trigonal basal face for the CsBr + EuBr 3 + H 2 O system at 298.15 K. The ion concentration of equilibrium liquid phase and the wet residue are shown as mass percent. Figure 2 displays the corresponding phase diagram.…”

“…The solubility of the CsBr + EuBr 3 + H 2 O system was investigated according to ref . The starting materials of CsBr, EuBr 3 ·5.97H 2 O, and H 2 O were mixed at different mass ratios.…”

“…Some potential upconversion materials, such as Er 3+ -doped RbGd 2 C1 7 and RbGd 2 Br 7 ; Cs 3 Yb 2 Cl 9 and Cs 3 Yb 2 Br 9 ; Cs 3 Y 2 Br 9 (10% Dy 3+ and Cs 3 Dy 2 Br 9 ); Cs 3 Er 2 X 9 (X = Cl, Br, I); and Er 3+ in Cs 3 Lu 2 Br 9 , were synthesized by means of the Bridgman technique − or improved Meyer method . In order to prepare the alkali metal bromide/rare-earth metal bromide compounds by phase equilibrium method and acquire the solubility of cesium bromide and rare-earth bromide at 298.15 K in H 2 O or HBr (∼12 mass %)–H 2 O medium, the phase equilibria for CsBr + REBr 3 + H 2 O (RE = La, Ce, Pr, Nd, Sm, Er, and Tm) ternary systems and CsBr + REBr 3 + HBr (∼13%) + H 2 O (RE = La, Ce, Pr, Nd, Sm, Dy, Er, and Tm) quaternary systems were reported continuously, − and the related research on rare-earth halide in aqueous media was compiled exhaustively . These phase diagrams were highly valuable for researchers to learn the phase equilibrium relationship of CsBr and REBr 3 in aqueous systems.…”

(Solid + liquid) equilibria for the ternary system (CsBr + LnBr3+ H2O) (Ln = Pr, Nd, Sm) at T= 298.2 K and atmospheric pressure, thermal and fluorescent properties of Cs2LnBr5·10H2O

“…The phase equilibria of binary systems (LnBr 3 + CsBr) (Ln = La, Ce, Pr, Tb, Dy) [5][6][7][8][9], ternary systems (CsBr + LnBr 3 + H 2 O) (Ln = La, Ce) [10] and quaternary systems (CsBr + LnBr 3 + HBr ($13 %) + H 2 O) (Ln = La, Ce, Pr, Nd, Sm, Dy) [11][12][13][14][15][16] were reported previously, and relevant results of rare earth metal halide in aqueous systems were evaluated importantly [17][18]. These studies provided the phase diagrams for scientists and engineers.…”