Chemical nature of giant strain in Mn-doped 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 lead-free ferroelectric single crystals

Giant bipolar and unipolar strains i.e. S-max > 0.5%, epsilon(max)/E-max > 1000 pm V-1 have been observed in Mn-doped Na0.5Bi0.5TiO3-6BaTiO(3) single crystals after being annealed. Temperature-dependent impedance spectra were studied and activation energies of oxygen vacancies were calculated accordingly. The two different binding energies present in X-ray photoelectron spectra for Na and Bi were assigned to different coordinate environments. However, titanium exhibits only one oxidation state (e.g. Ti4+). The site occupation and valence fluctuation of Mn were characterized by electric paramagnetic resonance spectra. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.