LAUSR

The Fe-doped lead-free 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 single crystal, reported in the previous work, which exhibited giant piezoelectric strain response (normalized strain constant up to ∼1300 pm/V) and a large quasi-static piezoelectric constant d33 of ∼600 pC/N, was investigated here with the emphasis on the domain structure so as to understand the nanoscale mechanism responsible for the giant strain response. Based on in-plane and out-of-plane piezoresponse force microscopy, it was found that Fe ion doping induced domain evolution from macrodomains of several micrometers to nanodomains of tens of nanometers. High-resolution transmission electron microscopy was adopted to give an insight into the fine domain structure after Fe doping. The domain evolution under an in situ electric field was further studied, and the results indicated that the giant strain response originated not only from the polarization rotation around the morphotropic phase boundary but also from the domain contribution.