Abstract
(1 − x) (Bi0.49Na0.49Ca0.02TiO3)-xCaHfO3 (BCNTH-x, x = 0.01, 0.02, 0.03, 0.035, 0.04) systems were prepared by solid-state reaction method. Their microstructures, dielectric/piezoelectric/ferroelectric properties and impedance spectroscopy were investigated. All compositions demonstrated a single orthorhombic structure with Pbnm space group. Temperature-dependent permittivity curves displayed one anomaly, which shifts to low temperature from 278 to 208 °C with increased CaHfO3 content, because of the replacement of Hf4+ for Ti4+ at the B-site that reduced B-site cation ordering. Analysis of dielectric and ferroelectric properties indicated that a crossover from typical ferroelectrics to relaxor ferroelectrics occurred in BCNTH-0.03 and BCNTH-0.035 ceramics. The largest electrostrictive strain of 0.22% and the lowest coercive field of 37.7 kV/cm were achieved in BCNTH-0.035 and BCNTH-0.03 ceramics under 100 kV/cm, respectively. Ferroelectric domain and domain wall were fitted by impedance complexes, and the corresponding activation energy was 0.46 and 1.18 eV, which may be correlated to the combination of motion of the first ionization of oxygen vacancies and doubly ionized oxygen vacancies, respectively.
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