Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium)₃[Sb₂Cl₉]

Abstract

Perovskite-like materials exhibit desirable photophysical and electric properties that make them suitable for a remarkable breadth of applications in electronics and physics. In this contribution, we report on the multiphase ferroelectric and ferroelastic phenomena in a pyrrolidinium-based hybrid metal–organic material: (C4H8NH2)3[Sb2Cl9]. The title compound is the first pyrrolidinium derivative within the halobismuthates­(III) and haloantimonates­(III) families that is featured by the ferroelectric property. From a structural point of view, the crystal structure is built of [Sb2Cl9]3– ∞ perovskite-like layers, interdigitated by layers of pyrrolidinium cations. The rich solid-state dynamics of pyrrolidinium cations endowed (C4H8NH2)3[Sb2Cl9] with a complex sequence of temperature-dependent phase transitions. Remarkably, polar properties have been found to occur in all six phases, including room-temperature Phase I. Insights from variable-temperature single-crystal X-ray diffraction, dielectric spectroscopy, and T1 spin–lattice relaxation measurements revealed the general mechanism of most phase transitions, as related to the progressive ordering of nonequivalent pyrrolidinium cations. Noncentrosymmetry is probed by room-temperature second harmonic generation (SHG), while the ferroelectric property was evidenced through P(E) and dielectric measurements. The experimental values of spontaneous polarization were justified and analyzed in the context of theoretical values derived from quantum-chemical calculations. Optical measurements show that the integrity of the sample survives all of the phase transitions, despite sometimes significant deformations of the unit cell. The changes of symmetry associated with structural phase transitions are accompanied by an intriguing evolution of the ferroelastic domain structure with temperature.

Ferroelastic Hysteresis in Thin Films of Methylammonium Lead Iodide

“…[16][17][18][19] This phenomenon is common in a variety of materials, such as zirconia 20 or oxide and fluoride perovskites, 21,22 and has been increasingly investigated in halide perovskites. [23][24][25][26][27][28][29][30][31][32] At elevated temperatures many APbX3 materials have higher symmetry, but as the material cools the R4 + phonon mode condenses, inducing permanent out-of-phase tilting of the BX6 octahedra and a spontaneous strain in the material. [33][34][35][36][37] The strain magnitude is lowered by transition to a lower symmetry phase, which in MAPbI3 is the cubic Pm-3m to tetragonal I4/mcm transition.…”

Recent Advancements in Nontoxic Halide Perovskites: Beyond Divalent Composition Space

“…It was found that (C 4 H 8 NH 2 ) 3 [Sb 2 Cl 9 ] has a trigonal R 3 m crystal structure and it is built up of [Sb 2 Cl 9 ] 3– infinite layers, composed of corner-sharing SbCl 6 octahedra, and pyrrolidinium counterions balance the negative charge of the layers. 43 2D and 3D materials are more desirable for photovoltaic applications than 0D materials given their lower band gap and smaller exciton banding energy. The optoelectronic properties of perovskites can be changed with tuning by halide and A- and B-site substitution.…”

Correlation between crystal structures and polar (ferroelectric) properties of hybrids of haloantimonates(iii) and halobismuthates(iii)

“…two-dimensional (2D) layers (honey-comb like corrugated sheets) (Fig. 3(b)); 72,[77][78][79][80][81][82][83][84][85][86][87][88][89] •. discrete bioctahedra (0D) (Fig.…”