Effect of growth temperature on the microstructural properties of 0.95Na_0.5Bi_0.5TiO₃–0.05BaTiO₃ films prepared on MgO (0 0 1) substrates

Lead-free 0.95(Na_0.5Bi_0.5)TiO₃–0.05BaTiO₃ (NBT-BT) piezoelectric films have been successfully fabricated by high-pressure magnetron sputtering deposition technique on (0 0 1)-oriented MgO substrates at 800 °C and 900 °C, respectively. By advanced electron microscopy techniques, the orientation relationship of (0 0 1)[1 1 0]_film//(0 0 1)[1 0 0]_MgO and (0 0 1)[1 0 0]_film//(0 0 1)[1 0 0]_MgO is determined for the NBT-BT/MgO heterostructures prepared at 800 °C and 900 °C, respectively. In comparison, a high density of zigzag-typed planar defects appear in the film prepared at 900 °C. At the semi-coherent interfaces, periodic dislocation arrays form to relax the film-substrate misfit strain. In particular, the formation of both (a/2) 〈0 1 0〉 -type and (a/2) 〈011-〉 -type interfacial dislocations facilitates the growth of NBT-BT films on rough MgO substrates at 900 °C. Our findings indicate that the mode of film growth and microstructure for NBT-BT films prepared on MgO substrates can be tuned by the growth temperature.