IMF2017

Relaxor ferroelectric sodium bismuth titanate‒barium titanate [92.5%(Bi_0.5Na_0.5)TiO₃ - 7.5%BaTiO₃ (BNB7.5T)] solid solution co-doped with 2 mol% strontium (Sr) and 0.1 mol% manganese (Mn) have shown enhanced stability of the material properties and piezoelectric responses, which show a large electric-field induced linear strain behavior. Sr and Mn co-doped BNB7.5T (BNB7.5T-Sr-Mn) crystals were grown by self-flux method. The as-grown BNB7.5T-Sr-Mn crystals show uniform color with dimensions around centimeter. Synchrotron X-ray diffraction (XRD) was used to measure temperature-dependent phase structure. High-resolution transmission electron microscope (TEM) was used to analyze microstructures and symmetries of unit cell. Dielectric permittivity, polarization hysteresis loop, strain vs E field, and piezoelectric coefficient d₃₃ were measured to analyze dielectric, ferroelectric, and strain properties. The results showed that BNB7.5T-Sr-Mn crystals have a coexistence phase of R3c and P4bm symmetries. Temperature-dependent dielectric permittivity and polarization loops of BNB7.5T-Sr-Mn crystals exhibited an ergodic relaxor behavior. The curves of strain vs. E field display a strain up to 0.49% at room temperature, which result mainly from the relaxor‒ferroelectric phase transition and electrostrictive response. Temperature-dependent P-E and D-T curves of BNB7.5T-Sr-Mn crystals show that the depolarization temperature T_d shifts toward lower temperature. Temperature-dependent S-E curves for BNB7.5T-Sr-Mn displayed a giant strain of 0.59% at 150 ^oC, indicating that BNB7.5T-Zr-Mn crystals possess excellent thermal stability and can be used as environmental friendly piezoelectric actuators.