Intercalation-driven ferroelectric-to-ferroelastic conversion in a layered hybrid perovskite crystal.

Wu, Zhenyue; Li, Shunning; Yousry, Yasmin Mohamed; Wong, Walter P D; Wang, Xinyun; Ma, Teng; Chen, Zhefeng; Shao, Yan et al. · Nat Commun · 2022

basic_science · Level V

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Abstract

Two-dimensional (2D) organic-inorganic hybrid perovskites have attracted intense interests due to their quantum well structure and tunable excitonic properties. As an alternative to the well-studied divalent metal hybrid perovskite based on Pb<sup>2+</sup>, Sn<sup>2+</sup> and Cu<sup>2+</sup>, the trivalent metal-based (eg. Sb<sup>3+</sup> with ns2 outer-shell electronic configuration) hybrid perovskite with the A<sub>3</sub>M<sub>2</sub>X<sub>9</sub> formula (A = monovalent cations, M = trivalent metal, X = halide) offer intriguing possibilities for engineering ferroic properties. Here, we synthesized 2D ferroelectric hybrid perovskite (TMA)<sub>3</sub>Sb<sub>2</sub>Cl<sub>9</sub> with measurable in-plane and out-of-plane polarization. Interestingly, (TMA)<sub>3</sub>Sb<sub>2</sub>Cl<sub>9</sub> can be intercalated with FeCl<sub>4</sub> ions to form a ferroelastic and piezoelectric single crystal, (TMA)<sub>4</sub>-Fe(iii)Cl<sub>4</sub>-Sb<sub>2</sub>Cl<sub>9</sub>. Density functional theory calculations were carried out to investigate the unusual mechanism of ferroelectric-ferroelastic crossover in these crystals.