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

• Bi2O3 addition could promote the grain growth in Sr0.4Ba0.6Nb2O6 ceramics.
• Doping Bi2O3 could improve the dielectric constant and lower the dielectric loss.
• The dielectric characteristics of doping Bi2O3 samples showed relaxation behavior.
• The P–E hysteresis loops for doping Bi2O3 ceramics became slimmer.

(1 − x) Sr0.4Ba0.6Nb2O6–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 Sr0.4Ba0.6Bi2Nb2O9 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 (Pr) and coercive field (Ec).