[C5H12N]CdCl3: an ABX3 perovskite-type semi-conducting switchable dielectric phase transition material

A new organic-inorganic ABX(3) perovskite-type semiconducting hybrid, N-methylpyrrolidinium trichlorocadmate (MPCC), has been synthesized. It is found that MPCC exhibits semiconducting behaviour with an optical bandgap of similar to 4.65 eV, as well as remarkable dielectric switching properties. It displays a structural phase transition (SPT) at T-c = 254 K, being confirmed by DSC and specific heat measurements. Dielectric measurements display distinct step-like anomalies around Tc, suggesting MPCC as a switchable dielectric material. Variable temperature single-crystal X-ray diffraction reveals that symmetry-breaking occurs from Pnma (at 280 K, > T-c) to P2(1)/c (at 230 K, < T-c), which is attributed to the ordering of the disordered N-methylpyrrolidinium (MP) cation. The most distinct difference between its low-and high-temperature structures is the order-disorder dynamics of the MP cation, which mainly contribute to the SPT and switchable dielectric activities of MPCC. This finding paves a new way for designing multi-featured ABX(3)-type SPT hybrids by choosing disordered cationic moieties.