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-CdCl2-H2O and CsBr-CdBr2-H2O were studied at T = 298.1 K. In the phase diagram of the system CsCl-CdCl2-H2O, the solid -phases of CsCdCl3 and Cs2CdCl4, besides CsCl and CdCl2.2.5H(2)O, were discovered. The phase diagram of the system CsBr-CdBr2-H2O contains five crystallization fields for the solid phases CdBr2.4H(2)O, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 and CsBr. The new solid phases of CsCdCl3 and CsCdBr3 are congruently soluble, and Cs2CdCl4, Cs5Cd2Br9 and Cs3CdBr5 are incongruently soluble in the aqueous system. The experimental solubility data and phase diagrams 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 CsCdCl3, Cs2CdCl4, CsCdBr3, Cs5Cd2Br9, Cs3CdBr5 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.

Automated summary

Using an isothermal equilibrium method, the phase equilibrium of the ternary systems CsCl-CdCl2-H2O and CsBr-CdBr2-H2O were studied, and new solid phases were discovered. The experimental results show the potential practical application of the obtained cadmium-based halide perovskite.