Lead-Free Hybrid Organic-Inorganic Ferroelectric: (3,3-Difluoropyrrolidinium) 2 ZnCl 4 ·H 2 O.

Hybrid organic-inorganic ferroelectrics (HOIFs) have a wide range of applications in the optoelectronic field in terms of rich optoelectronic properties. Particularly, lead-free HOIFs have attracted extensive attention due to their environmental friendliness, low heavy metal toxicity, and low synthesis cost. However, there are few reports about Zn-based HOIFs due to their uncontrollable ferroelectric synthesis and other reasons. Here, we designed and synthesized a zinc-based zero-dimensional (3,3-difluoropyrrolidine) 2 ZnCl 4 ·H 2 O ( DFZC ) single crystal, which undergoes a phase transition from ferroelectric to paraelectric phase (space group from Pna 2 1 to Pnma ) at 295.5 K/288.9 K during the heating/cooling process. The systematic study shows that the ferroelectric phase transition is a displacive type. The ferroelectric hysteresis loop of DFZC was obtained by the double-wave method and the Sawyer-Tower method, which has a spontaneous polarization ( P s ) of ∼0.4 μC/cm 2 . This work reveals the strategy to design new zinc-based lead-free HOIFs for potential applications in optoelectronic fields.