Order–Disorder Transition of a Rigid Cage Cation Embedded in a Cubic Perovskite

Abstract

The structure and properties of organic–inorganic hybrid perovskites are impacted by the order–disorder transition, whose driving forces from the organic cation and the inorganic framework cannot easily be disentangled. Herein, we report the design, synthesis and properties of a cage-in-framework perovskite AthMn(N3)3, where Ath+ is an organic cation 4-azatricyclo[2.2.1.02,6]heptanium. Ath+ features a rigid and spheroidal profile, such that its molecular reorientation does not alter the cubic lattice symmetry of the Mn(N3)3− host framework. This pure order–disorder transition is well characterized by NMR, crystallography, and calorimetry, and associated with the realignment of Ath+ dipole from antiferroelectric to paraelectric. As a result, an abrupt rise in the dielectric constant was observed during the transition. Our work introduces a new family of perovskite structures and provides direct insights to the order–disorder transition of hybrid materials.

Tunable Dielectric Switching of (Quinuclidinium)[MnCl4] Hybrid Compounds

“…Most of the synthesized hybrid crystals undergo reversible structural PTs. It is found that both order–disorder transformations of polar organic cations and weak displacements of inorganic frameworks make contributions to its switchable dielectric properties. , Particularly, recent scientific reports have revealed that for hybrids with spherical molecules such as dabco (1,4-diazabicyclo[2.2.2]­octanium) or Q (quinuclidinium), a dynamic rotation or reorientation freezing involves interesting physicochemical properties and structural PT. , The search for good switchable dielectric materials is nontrivial, mainly due to satisfying simultaneously different requirements, e.g., attractive working temperature, sharp steplike phase transition, small-frequency dependence as well as easy and profitable technology.…”