Electric-field-induced Local Distortion and Large Electrostrictive Effects in Lead-Free NBT-based Relaxor Ferroelectrics

In this work, the (0.94-x)(Na0.5Bi0.5)TiO3-0.06Ba(Zr0.05Ti0.95)O-3-x(Sr0.8Bi0.1 square(0.1))TiO2.95 (NBT-BZT-xSBT) ternary relaxor ferroelectrics were chosen as the studied compositions, and the in-situ electric-field-dependent Raman spectra and PFM measurements were performed to systematically investigate the structural distortion and local polarization switching. Results showed that the SBT enhances the relaxor degree and depresses the field-induced local distortion. The higher field required initially for obtaining polarization saturation with increasing SBT concentration is related to overcoming the hindrance posed by the local structural heterogeneity. Most intriguingly, a giant and temperature-insensitive electrostrictive effect (Q(33) = 0.035 m(4)/C-2, RT similar to 120 degrees C: variation less than 2%) was achieved in SBT5 composition. Such performance is one of the best values ever reported on lead-free and lead-based electrostrictive materials. A modified Landau model was proposed to phenomenologically elaborate the underlying mechanisms. Our findings illustrate that understanding structural changes at multiple length scale will be helpful for designing novel lead-free piezoceramics with high performance.