Visualization of domain structure and piezoelectric energy harvesting in a ferroelectric metal-ligand cage.

The ferroelectric behaviour of an octahedral cage [[Ni 6 (H 2 O) 12 (TPTA) 8 ]·(NO 3 ) 12 ·36H 2 O] (1) exhibiting high remnant polarization of 25.31 μC cm -2 is discovered. For the first time, clear domain structures and the characteristic electromechanical responses are demonstrated using piezoresponsive force microscopy for a thin film of 1. Owing to its mechanical energy conversion capability, polymer composites of 1 were employed as efficient piezoelectric nanogenerators.