In Search of a Double Perovskite in the Phase Triangle of Bromides CsBr-CuBr-InBr₃

New bromide compounds A₂B^IB^IIIBr₆ with a double perovskite structure provide variety and flexibility of optoelectronic properties, and some of them are of poor toxicity in comparison with such popular lead halides. The promising compound with a double perovskite structure was proposed recently for the ternary system of CsBr-CuBr-InBr₃. Analysis of phase equilibria in the CsBr-CuBr-InBr₃ ternary system showed stability of the quasi-binary section of CsCu₂Br₃-Cs₃In₂Br₉. Formation of the estimated phase Cs₂CuInBr₆ by melt crystallization or solid-state sintering was not observed, most likely, as a result of higher thermodynamic stability of binary bromides CsCu₂Br₃ and Cs₃In₂Br₉. The existence of three quasi-binary sections was observed, while no ternary bromide compounds were found.