Ferroelectric and piezoelectric properties of lead-free BaTiO3 doped Bi0.5Na0.5TiO3 thin films from metal-organic solution deposition

Highlights: ► Lead-free BNT–BT thin films from an optimized metal-organic solution deposition. ► Phase and microstructure evolution with annealing temperature. ► A relatively low leakage current density. ► Good dielectric constant of 613 at a frequency of 1 kHz. ► High remanent polarization and piezoelectric constant comparable to PZT thin films. - Abstract: Lead-free 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 (BNT–BT) piezoelectric thin films were prepared by metal-organic solution deposition onto a Pt/Ti/SiO2/Si substrate. A dense and well crystallized thin film with a perovskite phase was obtained by annealing these films at 700 °C. Atomic force microscopy showed that these films were smooth and crack-free with an average grain size on the order of 200 nm. Thin films of 356 nm thickness exhibited a small signal dielectric constant and a loss tangent at 1 kHz of 613 and 0.044, respectively. Ferroelectric hysteresis measurements indicated a remanent polarization value of 21.5 μC/cm2 with a coercive field of 164.5 kV/cm. The leakage current density of the thin film was 4.08 × 10−4 A/cm2 at an applied electric field of 200 kV/cm. A typical butterfly-shaped piezoresponse loop was observed and the effective piezoelectric coefficient (d33) of the BNT–BT thin film was approximately 51.6 pm/V.