Preparation and electrical properties of Bi0.5Na0.5TiO3-BaTiO3-KNbO3 lead-free piezoelectric ceramics

Research highlights: → Bi0.47Na0.47Ba0.06TiO3-KNbO3 ceramics exhibit excellent piezoelectric properties. → The optimized properties of the ceramics: d33 = 195 pC/N; kt = 58.9; Qm = 113; Ec = 19.5 kV/cm. → KNbO3 has diffused into the Bi0.47Na0.47Ba0.06TiO3 lattices to form a new solid solution. → Macro-micro domain switching occurs at depolarization temperature Td. - Abstract: Lead-free (1 - x)Bi0.47Na0.47Ba0.06TiO3-xKNbO3 (BNBT-xKN, x = 0-0.08) ceramics were prepared by ordinary ceramic sintering technique. The piezoelectric, dielectric and ferroelectric properties of the ceramics are investigated and discussed. The results of X-ray diffraction (XRD) indicate that KNbO3 (KN) has diffused into Bi0.47Na0.47Ba0.06TiO3 (BNBT) lattices to form a solid solution with a pure perovskite structure. Moderate additive of KN (x ≤ 0.02) in BNBT-xKN ceramics enhance their piezoelectric and ferroelectric properties. Three dielectric anomaly peaks are observed in BNBT-0.00KN, BNBT-0.01KN and BNBT-0.02KN ceramics. With the increment of KN in BNBT-xKN ceramics, the dielectric anomaly peaks shift to lower temperature. BNBT-0.01KN ceramic exhibits excellent piezoelectric properties and strong ferroelectricity: piezoelectric coefficient, d33 = 195 pC/N; electromechanical coupling factor, kt = 58.9 and kp = 29.3%; mechanical quality factor, Qm = 113; remnant polarization, Pr = 41.8 μC/cm2; coercive field, Ec = 19.5 kV/cm.