Structure and Piezoelectricity Due to B Site Cation Variation in AB n + Cl n +2 Hybrid Histammonium Chlorometallate Materials.

To provide new insights for understanding the influence of B site cations on the structure in chlorometallate materials of the form AB n + Cl n +2 , we report novel organic-inorganic hybrid metallates (OIHMs) incorporating histammonium (HistNH 3 ) dications and various transition-metal and main group B site cations. Single crystals of OIHMs with the basic formula (HistNH 3 M n + Cl n +2 , M = Fe, Co, Ni, Cu, Zn, Cd, Hg, Sb, Sn, Pb, Bi) were grown and their structures characterized by single-crystal X-ray crystallography. HistNH 3 CoCl 4 , HistNH 3 ZnCl 4 , and HistNH 3 SbCl 5 were crystallized in a non-centrosymmetric space group and were subsequently studied with piezoresponse force microscopy (PFM). While bulk measurements of crystals and poly(vinylidene difluoride) (PVDF)/metallate composite films exhibited low bulk response values, the surface-measured local response values using PFM were 5.17 pm/V for HistNH 3 CoCl 4 , 22.6 pm/V for HistNH 3 ZnCl 4 , and 2.9 pm/V for HistNH 3 SbCl 5 compared with 2.50 pm/V for PVDF reference samples. The magnitudes of the d 33 coefficient, net dipole, and cation-Cl bond dipole obtained from the density functional theory calculations confirm the higher response in HistNH 3 ZnCl 4 compared to HistNH 3 CoCl 4 . Density of states and crystal orbital Hamilton population analysis indicate that the higher net dipole in HistNH 3 ZnCl 4 compared to HistNH 3 CoCl 4 is due to the lower hybridization of the M-Cl bond.