Enhanced piezoelectricity and reduced leakage current of a novel (1 − x )Bi 0.5 Na 0.5 TiO 3 – x (Sr 0.7 Bi 0.2 □ 0.1 )TiO 3 thin film

Lead-free (1− x )Bi 0.5 Na 0.5 TiO 3 – x (Sr 0.7 Bi 0.2 □ 0.1 )TiO 3 ( x = 0.0, 0.1, 0.2 and 0.3, denoted as BNT– x SBT) thin films were deposited on Pt(111)/Ti/SiO 2 /Si substrates by the sol–gel method, and their microstructure and dielectric, ferroelectric and piezoelectric properties were investigated in detail. All thin films present a single perovskite structure as demonstrated. In particular, appropriate Mn doping modifies the concentration of oxygen vacancies in thin films, resulting in a marked decline in leakage current. In this way, an ultra-high inverse piezoelectric coefficient ( d 33 * ∼144.11 pm V −1 ) can be obtained from a 0.8BNT–0.2SBT thin film, and a maximum polarization P m of 46.88 μC cm −2 is observed under an electric field of 700 kV cm −1 . Meanwhile, a BNT–SBT thin film has flexible dielectric tunability. All results strongly suggest that the ultra-high piezoelectric property of BNT–0.2SBT is derived from the ferroelectric-to-relaxor transition. As described, this work indicates that the BNT–SBT thin film is an ideal lead-free piezoelectric substituted material. Moreover, BNT–SBT is a novel system of thin films, which has a great development prospect.