(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. (November 2015)

• Record Type: Journal Article
• Authors: Qiao, Zhan-Ping; Li, Zhao-Wan; Chen, Xin; Dang, Yuan-Lin; Yang, Qi-Chao
• Is Part Of: Journal of chemical thermodynamics. Volume 90(2015:Nov.)
• Page Start: 209
• Page End: 215
• Publication Date: 2015-11
• Subjects: Phase diagram -- Cesium bromide -- Rare earth bromides -- Standard molar enthalpy of formation -- Fluorescent property; Thermodynamics -- Periodicals; Thermochemistry -- Periodicals; Thermodynamique -- Périodiques; Thermochimie -- Périodiques; Thermochemistry; Thermodynamics; Periodicals; 541.369
• DOI: 10.1016/j.jct.2015.07.004
• Languages: English
• ISSNs: 0021-9614

Abstract

Graphical abstract: Highlights: Solubility was measured for (CsBr + REBr3 + H2 O) (RE = Pr, Nd, Sm) systems at T = 298.2 K. The phase diagrams were plotted. Three compounds Cs2 REBr5 ·10H2 O were characterized by enthalpies of formation and their fluorescent properties. Abstract: The (solid + liquid) phase equilibria of the ternary systems (CsBr + LnBr3 + H2 O) (Ln = Pr, Nd, Sm) at T = 298.2 K were studied by the isothermal solubility method. The solid phases formed in the systems were determined by the Schreinemakers wet residues technique, and the corresponding phase diagrams were constructed based on the measured data. Each of the phase diagrams, with two invariant points, three univariant curves, and three crystallization regions corresponding to CsBr, Cs2 LnBr5 ·10H2 O and LnBr3 ·nH2 O ( n = 6, 7), respectively, belongs to the same category. The new solid phase compounds Cs2 LnBr5 ·10H2 O are incongruently soluble in water, and they were characterized by chemical analysis, XRD and TG-DTG techniques. The standard molar enthalpies of solution of Cs2 PrBr5 ·10H2 O, Cs2 NdBr5 ·10H2 O and Cs2 SmBr5 ·10H2 O in water were measured to be (52.49 ± 0.48) kJ · mol −1, (49.64 ± 0.49) kJ · mol −1 and (50.17 ± 0.48) kJ · mol −1 by microcalorimetry under the condition of infinite dilution, respectively, and their standard molar enthalpies of formation were determined as being −(4739.7 ± 1.4) kJ · mol −1, −(4728.4 ± 1.4) kJ · mol −1 and −(4724.4 ± 1.4) kJ · mol −1, respectively. The fluorescence excitation and emission spectra of Cs2 PrBr5 ·10H2 O, Cs2 NdBr5 ·10H2 O and Cs2 SmBr5 ·10H2 O were measured. The results show that the upconversion spectra of the three new solid phase compounds all exhibit a peak at 524 nm when excited at 785 nm.