Structural Phase Transitions and Dielectric Switching in a Series of Organic-Inorganic Hybrid Perovskites ABX3 (X=ClO_4~- or BF_4~-)

摘要

A series of organic-inorganic hybrid perovskites ABX_3 (A=diprotonated 1,4-diazabicyclo[2.2.2]octane or piperazine; B=Na~+ or K~+; X=ClO_4~- or BF_4~-) has been synthesized. They feature a cubic cage-like host-guest structures of which A is the cationic guest residing in the anionic cage B_8X_(12), B is the vertex of the cage with variable coordination numbers between six and twelve, and X is the bridging ligand with mono-and/or bidentate coordination modes. The extended Goldschmidt tolerance factor t is used to describe the phase stability of the compounds. Differential scanning calorimetry, variable-temperature structural analyses, and dielectric measurements reveal that order-disorder transitions of the A guest and/or X bridging ligand are supposed to be responsible for structural phase transitions and dielectric switching in the compounds.