Ternary chlorides in the systems ACl/HoCl3 (A = Cs, Rb, K)

Article abstract of DOI:10.1016/S0925-8388(96)03119-2

The phase diagrams of the pseudo-binary systems ACl/HoCl₃ (A = Cs, Rb, K) were investigated by DTA and XRT. The existence of compounds A₃HoCl₆, Cs₂HoCl₅, Cs₃Ho₂Cl₇ and AHo₂Cl₇ could be confirmed. Additionally, the 2:1-compounds Rb₂HoCl₅ (Cs₂DyCl₅-structure) and K₂HoCl₅(K₂PrCl₅-structure) were found. By solution enthalpy and e.m.f vs. T measurements in galvanic chlorine cells for solid electrolytes, the thermodynamic functions for the formation from ACl and HoCl₃ and for the formation from the compounds adjacent in the phase diagrams were measured. The compounds A₃HoCl₆ could be prepared also from acetic acid solutions. From aqueous solutions, the ternary halides Cs₄HoCl₇ and Cs₃HoCl₆ crystallizing in the space group Pbcm were prepared. Anhydrous HoCl₃ can be obtained comfortably from holmium formiate at approximately 300 °C in an HCl gas stream.