Polar Nature of (CH3NH3)3Bi2I9Perovskite-Like Hybrids.
High-quality single crystals of perovskite-like (CH3NH3)3Bi2I9hybrids have been synthesized, using a layered-solution crystal-growth technique. The large dielectric constant is strongly affected by the polar ordering of its constituents. Progressive dipolar ordering of the methylammonium cation upon cooling below 300 K gradually converts the hexagonal structure (space group P63/mmc) into a monoclinic phase (C2/c) at 160 K. A well-pronounced, ferrielectric phase transition at 143 K is governed by in-plane ordering of the bismuth lone pair that breaks inversion symmetry and results in a polar phase (space group P21). The dielectric constant is markedly higher in the C2/c phase above this transition. Here, the bismuth lone pair is disordered in-plane, allowing the polarizability to be substantially enhanced. Density functional theory calculations estimate a large ferroelectric polarization of 7.94 μC/cm2along the polar axis in the P21phase. The calculated polarization has almost equal contributions of the methylammonium and Bi3+lone pair, which are fairly decoupled.
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Machteld E
ME
Kamminga
Consiglio Nazionale della Ricerche (CNR-SPIN) , Via Vetoio 10, L'Aquila 67100, Italy.
Alessandro
A
Stroppa
Consiglio Nazionale della Ricerche (CNR-SPIN) , Via Vetoio 10, L'Aquila 67100, Italy.
Silvia
S
Picozzi
Research Centre for Thermogravimetric and Calorimetric Research, St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
Mikhail
M
Chislov
Research Centre for Thermogravimetric and Calorimetric Research, St. Petersburg State University , 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.|Institute of Chemistry, St. Petersburg State University , Universitetskiy prospect 26, Petrodvoretz, St. Petersburg 198504, Russia.
Irina A
IA
Zvereva
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Jacob
J
Baas
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Auke
A
Meetsma
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Graeme R
GR
Blake
Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, Groningen 9747 AG, The Netherlands.
Thomas T M
TT
Palstra