Thermal properties and phase transitions in (NH4)3ZrF7.

Highlights: [•] (NH4)3ZrF7 undergoes the succession of six ferroelastic phase transitions. [•] The transformation between two cubic phases Fm-3m↔F23 is suggested at T 0. [•] Excess entropy does not correspond to strong disorder model of cubic structure. [•] The stability of all phases except G4 increases with pressure increase. [ABSTRACT FROM AUTHOR]