Domain Structures and Temperature Induced Phase Transitions in Perovskite Molecular 3-Ammonioquinuclidinium-NH4Cl3

Molecular ferroelectric 3-ammonioquinuclidinium-NH4Cl3 (3-AP-NH4Cl3) crystals were prepared. DSC-C-P-TG curves were studied and a small endothermic peak was discovered at 146 degrees C without obvious mass change. Dielectric properties were measured and a sharp peak was found at 146 degrees C in the dielectric constant versus temperature curve. Temperature-dependent domain evolution was observed in situ by polarized light microscopy (PLM). The extinction-variation temperature range agreed well with the phase transition temperature that takes place in the dielectric measurement. This result further confirmed a phase transition from ferroelectric phase to paraelectric phase. A schematic diagram is also established to clarify the temperature induced phase transition. The shape change of free energy curve caused by temperature may result in the phase transition.