Lead-free hybrid ferroelectric material based on formamidine: [NH₂CHNH₂]₃Bi₂I₉

Abstract

Novel room-temperature ferroelectric crystals with complex sequences of phase transitions.

Reversible Phase Transition, Switchable Second‐Order Nonlinear Optical and Dielectric Properties in a Bismuth(III)‐Based Compound: (R)‐3‐(Fluoropyrrolidinium)2BiBr5

“…Recently, halogenometallate hybrid compounds have drawn much attention because of their rich conducting, photovoltaic, optical and electrical properties, together with easy processability. [17][18][19][20][21][22][23][24][25] They also show diverse structures varying from discrete mononuclear to three-dimensional framework. The metal ions and halogen ions in halogenometallate hybrid compounds play a virtual role in the change of the framework structures and the dynamic behavior of the guest.…”

“…The metal ions, as coordination center, display various coordination numbers (commonly from four to six) and geometries (tetrahedral, trigonal bipyramidal and octahedral). [23][24][25] At the same time, the halogen ions act as not only terminal ligands but also bridging ligands. As a result, numerous halogenometallate hybrid compounds had been built under the interplay of organic cation.…”

“…[24] Intriguing properties, such as ferroelectric, antiferroelectric, and dielectric transitions, have been extensively investigated. [3,6,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Besides, the H/F substitution, as a supplement to the isotopic effect, has also demonstrated a particularly useful idea in designing halogenometallate hybrid compounds with a switchable phase transition behavior. [24,26,27] Due to the different electronegativities between the H and F atoms, the H/F substituted products reduce the crystal symmetry while the structure remains basically unchanged and increase the possibility of the significant changes in the physical responses.…”

“…Recently, halogenometallate hybrid compounds have drawn much attention because of their rich conducting, photovoltaic, optical and electrical properties, together with easy processability . They also show diverse structures varying from discrete mononuclear to three‐dimensional framework.…”

“…The metal ions and halogen ions in halogenometallate hybrid compounds play a virtual role in the change of the framework structures and the dynamic behavior of the guest. The metal ions, as coordination center, display various coordination numbers (commonly from four to six) and geometries (tetrahedral, trigonal bipyramidal and octahedral) . At the same time, the halogen ions act as not only terminal ligands but also bridging ligands.…”