H/F substituted perovskite compounds with above-room-temperature ferroelasticity: [(CH3)4P][Cd(SCN)3] and [(CH3)3PCH2F][Cd(SCN)3]

Abstract

An organic–inorganic perovskite compound [(CH₃)₄P][Cd(SCN)₃] (1) and its fluorine-substituted product [(CH₃)₃PCH₂F][Cd(SCN)₃] (2) exhibit ferroelastic phase transitions above room temperature. The very close van der Waals radii of H and F atoms ensure isomorphism of the crystal structures. However, the higher phase transition temperature, stronger ferroelastic spontaneous strain value and dielectric properties of 2 can possibly be explained by differences in the electronegativity between F and H atoms.