Successive Phase Transitions and Dual Dielectric Switching in an Organic–Inorganic Hybrid Perovskite

Molecular phase transition compounds have become a hot research area in recent years because of their potential as functional materials, such as ferroelectrics, ferroelastics, dielectric switches, etc. However, materials combining switchable dielectric properties and ferroelasticity are still rare. Here, we reported an organic-inorganic hybrid perovskite, [CPtmp][Cd(SCN)₃] (1) ([CPtmp]⁺ is a cyclopentyltrimethylphosphonium cation), with a potential ferroelastic property. This material undergoes three structural phase transitions at 247/226, 335/312, and 349/341 K (upon heating/cooling). The successive phase transitions are mainly caused by the stepwise ordering of [CPtmp]⁺ cations and the concomitant deformation of [Cd(SCN)₃]^- anionic chains revealed by structural analyses, which triggers the double-step dielectric switching in 1 as well. These results would inspire further exploration on molecular dielectric switches with ferroelastic properties.