Ferroelectric and piezoelectric properties of lead-free Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-BaTiO3-thin films near the morphotropic phase boundary

Lead-free Bi0.5Na0.5TiO3 (BNT)-Bi0.5K0.5TiO3 (BKT)-BaTiO3 (BT) piezoelectric thin films with compositions near the morphotropic phase boundary (MPB) were deposited by metal-organic solution deposition on Pt/Ti/SiO2/Si (1 0 0) substrates. The compositional dependences of their microstructure and ferroelectric/piezoelectric properties were investigated. The results indicated that all the thin films have a single-phase perovskite structure and show outstanding electrical properties at room temperature. We found that the thin film with a composition of 0.884BNT-0.08BKT-0.036BT showed the best structural and electrical properties, with a dielectric constant, remnant polarization, and effective piezoelectric constant of ∼638, ∼27 μC/cm2 and ∼79 pC/N, respectively. We suggest that these superior properties are due to this sample's high degree of alignment of ferroelectric domains in the MPB region and largest grain size.