Ultrahigh ferroelectric response in Fe modified 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 single crystals

Single crystals of x at% Fe + 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO(3) (x%-Fe:NBBT5, x = 0.1, 0.2 and 0.5) with ultrahigh ferroelectric response were developed by introducing (Fe-Pi' - V-O(center dot center dot))(center dot) defect associations. The very large field-induced bipolar and unipolar strains, i.e., S-max similar to 1.1%, epsilon(max)/E-max similar to 1300 pm V-1, d(33) similar to 600 pC N-1 and permittivity tunability similar to 120%, demonstrate that these crystals are promising candidates as lead-free ferroelectrics. The presence of ferromagnetic properties further provides their new application potential as multiferroic materials. The defect chemistry and domain structure were studied systematically. The effects of microscopic defect functional centers on macroscopic properties were discussed in detail.