Enhanced piezoelectricity and reduced leakage current of a novel (1 − x)Bi0.5Na0.5TiO3–x(Sr0.7Bi0.2□0.1)TiO3 thin film

Abstract

Lead-free (1−x)Bi_0.5Na_0.5TiO₃–x(Sr_0.7Bi_0.2□_0.1)TiO₃ (x = 0.0, 0.1, 0.2 and 0.3, denoted as BNT–xSBT) thin films were deposited on Pt(111)/Ti/SiO₂/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 (d₃₃* ∼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.