Lattice evolution and enhanced piezoelectric properties of hydrothermally synthesised 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 nanofibers

Abstract

In this work, a facile low-temperature hydrothermal method accompanied by a moderate annealing process is introduced to synthesise highly crystallized lead-free piezoelectric 0.94(Bi_0.5Na_0.5)TiO₃–0.06BaTiO₃ (BNBT) nanofibers where sodium ions in the native (Bi_0.5Na_0.5)TiO₃ (BNT) lattice are substituted with larger barium ions. The BNBT nanofibers are typically 150–200 nm in diameter composed of a confirmed pure perovskite phase with the orientation of (101) along the fiber length direction. A rhombohedral lattice structure was verified by transmission electron microscopy measurements after introducing barium into the BNT structure. Solid-state ²³Na NMR evidenced a reduced disorder in the primary A site of the BNBT as compared to the BNT, along with the formation of additional Na environments, which were assigned to an inhomogeneous distribution of Ba in the system. A significant piezoelectric constant of d₃₃ = ∼26 ± 2 pm V⁻¹ in the diameter direction was found for these BNBT nanofibers.