Solubility Phase Diagrams of ternary systems of CsCl–CdCl2–H2O and CsBr–CdBr2–H2O at T = 298.1 K and the thermodynamic properties of the new solid phase compounds

Using an isothermal equilibrium method, the   phase   equilibrium of the ternary systems CsCl–CdCl 2 –H 2 O and CsBr–CdBr 2 –H 2 O were studied at T  = 298.1 K. In the   phase   diagram of the system CsCl–CdCl 2 –H 2 O, the solid   phases   of CsCdCl 3 and Cs 2 CdCl 4 , besides CsCl and CdCl 2 ·2.5H 2 O, were discovered. The   phase   diagram   of the system CsBr–CdBr 2 –H 2 O contains five crystallization fields for the solid   phases CdBr 2 ·4H 2 O, CsCdBr 3 , Cs 5 Cd 2 Br 9 , Cs 3 CdBr 5 and CsBr. The new solid   phases   of CsCdCl 3 and CsCdBr 3 are congruently soluble, and Cs 2 CdCl 4 , Cs 5 Cd 2 Br 9 and Cs 3 CdBr 5 are incongruently soluble in the aqueous system. The experimental solubility data and phase diagram s for the ternary systems show more practical application for the obtained cadmium-based halide perovskite. The five new solid phase have been analyzed by X-ray diffraction and thermogravimetry/derivative thermogravimetry. By measuring the standard molar enthalpies of solution of the compounds, the standard molar enthalpies of formation of CsCdCl 3 , Cs 2 CdCl 4 , CsCdBr 3 , Cs 5 Cd 2 Br 9 , Cs 3 CdBr 5 were determined to be –(873.3 ± 0.7) kJ·mol −1 , –(1325.6 ± 0.9) kJ·mol −1 , –(742.8 ± 0.7) kJ·mol −1 , –(2710.0 ± 1.3) kJ·mol −1 and –(1558.1 ± 1.0) kJ·mol −1 , respectively.