Microstructure and relaxor ferroelectric properties of Bi2O3-doped strontium barium niobate ceramics

(1 − x) Sr_0.4Ba_0.6Nb₂O₆–xBi₂O₃ (0.00 ≤ x ≤ 0.20) ceramics were prepared by conventional solid-state reaction method. The microstructure, dielectric properties and P–E hysteresis loops of ceramics were investigated via X-ray diffraction, scanning electron microscope (SEM), Agilent E4980A and modified Sawyer–Tower circuit, respectively. XRD results showed the obtained ceramics were of tungsten bronze structure, and second phase Sr_0.4Ba_0.6Bi₂Nb₂O₉ was detected at high doping concentration. SEM results showed suitable Bi₂O₃ addition could reduce the sintering temperature and assist the grain growth. The dielectric characteristics exhibited diffuse phase transition phenomena, which were verified by linear fitting of the modified Curie–Weiss law. Besides, the relaxor ferroelectric properties of ceramics followed the Vogel–Fulcher relationship well. The P–E hysteresis loops became slimmer with increasing the Bi₂O₃ addition, leading to a gradually decrease in both remnant polarization (P_r) and coercive field (E_c).