The effects of sintering atmosphere on microstructures and electrical properties of lead-free (Bi0.5Na0.5)TiO3-based ceramics

0.93(Bi0.5Na0.5)TiO3-0.07BaTiO3 (BNT-7BT) piezoelectric ceramics sintered in O2 and N2 have been investigated to understand the effects of sintering atmosphere in defects, microstructures, and dielectric properties. The BNT-7BT ceramics sintered in O2 and N2 exhibit a major pseudo-cubic structure with slight distortion from the cubic cell. The specimen sintered in N2 atmosphere shows larger grain sizes than the specimen sintered in O2. The X-ray photoelectron spectroscopy (XPS), SEM-EDS, and TEM-EDS suggest that specimen sintered in N2 atmosphere exhibits more ion vacancies. Leakage current measurements suggest more oxygen vacancies for specimen sintered in N2. A higher remnant polarization and lower coercive field were observed for specimen sintered in O2. Strain vs. E field (S-E) loops display higher E-field induced strain up to 0.256% and higher dielectric permittivity for specimen sintered in O2. This work suggests that sintering in the O-rich atmosphere can reduce defects and enhances ferroelectric, dielectric, and piezoelectric properties.