Features of Phase Formation in the CsOH–H₂SO₄–H₃PO₄–H₂O System and the Growth of the Cs₆(SO₄)₃(H₃PO₄)₄ Crystals

In this paper, the conditions of phase formation in the system CsOH–H2SO4–H3PO4–H2O are considered for the first time. The phase formation of Cs6(SO4)3(H3PO4)4 at t = 50 °C has been studied extensively. The main concentration boundary conditions for this compound are considered for the first time. The solubility congruence of Cs6(SO4)3(H3PO4)4 is shown. Conditions and approaches for obtaining crystals by isothermal evaporation and saturated solution temperature reduction methods are considered. The results of obtaining Cs6(SO4)3(H3PO4)4 crystals with maximum dimensions of ~20 mm are presented

Implementation of Phase Transitions in Rb₃H(SO₄)₂ under K Substitution

A series of solid acid compounds, representing the large family MmHn(AO4)(m + n)/2·yH2O (where M = K, Rb, Cs, NH4; AO4 = SO4, SeO4, HPO4, HAsO4), is characterized by high values of own proton conductivity, which arises as a result of a phase transition through the formation of a dynamically disordered hydrogen bond network. Such superprotonic phase transitions are observed, however, not for all compounds of the family and Rb3H(SO4)2 is one of them. The occurrence of superprotonic phase transitions has been experimentally demonstrated in the (KxRb1−x)3H(SO4)2 solid solutions through cation substitution. The high-temperature phases are unstable towards decomposition reaction, and their temperature range of existence is about 1–7 °C. The implementation of superprotonic transitions is discussed in terms of hydrogen bond lengths