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High-temperature ferroelastic phase transition in a perovskite-like complex: [Et₄N]₂[PbBr₃]₂

Huang, Yuan, Yang, Jie, Li, Zi-jian, Qian, Kun, Sao, Feng
RSC advances 2019 v.9 no.18 pp. 10364-10370
X-ray diffraction, ambient temperature, atomic force microscopy, bromides, cations, crystal structure, differential scanning calorimetry, lead, phase transition, tetraethylammonium compounds
A new lead-bromide hybrid organic–inorganic complex [Et₄N]₂[PbBr₃]₂ (Et = ethyl) was synthesized, and its crystal structures could be described as a distorted perovskite-like one (at room temperature phase and at high temperature phase) and a step-like dielectric anomaly was obtained at around 375 K upon heating and 367 K upon cooling. It underwent a reversible structural phase transition with the Aizu notation of 6/mmmF2/m belonging to one of the 94 species of ferroelastic phase transitions, displayed switchable dielectric behaviors triggered by the motion or reorientation of the tetraethylammonium cations and the displacement of Pb²⁺ and Br⁻ ions in a solid-state crystal. Ferroelastic domain walls were also observed in atomic-force microscopy. Differential scanning calorimetry, dielectric measurements and variable-temperature X-ray structure determinations indicated this complex exhibited a dielectric anomaly associated with the structural phase transition. All of these demonstrate its potential application as a temperature switchable molecular dielectric material in the ferroic-related field.