Structural Phase Transitions and Dielectric Switching in a Series of Organic-Inorganic Hybrid Perovskites ABX3 (X=ClO4- or BF4-)

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=ClO4- or BF4-) has been synthesized. They feature a cubic cage-like host-guest structures of which A is the cationic guest residing in the anionic cage B8X12, 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.