Switchable Dielectric Phase Transition with Drastic Symmetry Breaking in a Sn(IV)-Based Perovskite-Type Halide Semiconductor

A new tin(IV)-based perovskite-type hybrid semiconductor, bis(trimethyliodomethylammonium) hexachloridostannate(IV) ([TMIM](2)SnCl6), has been synthesized as a switchable dielectric phase transition material, featuring a zero-dimensional inorganic architecture of [SnCl6]2- octahedra and organic [TMIM] (+) cations. It is found that [TMIM](2),SnCl6 displays a reversible structural phase transition at 329 K, demonstrated by the differential scanning calorimetry (DSC) measurements. The dielectric constant exhibits remarkable steplike anomaly around the phase transition temperature (T-c), indicating switchable dielectric behaviors. Variable-temperature structure analyses disclose that the drastic symmetry breaking occurs with the structure transferring from Fm (3) over barm to C2/c by the temperature decreasing. The mechanism of such a transition is associated with the order-disorder transformation of organic ammonium and the displacement of the inorganic framework, which benefits from the discrete anionic architectures that provide enough space. Meanwhile, [TMIM](2)SnCl6 shows a semiconducting property with a wide optical bandgap of similar to 4.83 eV. This finding of the Sn(IV)-based metal halide with prominent phase transition and semiconducting behaviors will direct an executable pathway for designing novel multifunctional perovskite-type switchable materials.