Evidence of morphotropic phase boundary displacement in lead-free (Bi0.5Na0.5)1−xBaxTiO3 polycrystalline thin films

Abstract Lead-free (Bi 0.5 Na 0.5 ) 1 − x Ba x TiO 3 (BNBT) thin films with compositions at x = 0.055, 0.100, and 0.150 were prepared by chemical solution deposition on Pt/TiO 2 /SiO 2 /(100)Si substrates. The dielectric behavior of the films was studied, and the ferroelectric-antiferroelectric phase transition observed was used to situate the morphotropic phase boundary (MPB) for compositions with x ~ 0.100 (BNBT-10), a value that differs from that reported for bulk materials (BNBT-5.5). Extrinsic effects derived from the thin-film configuration (e.g., microstrains, residual stresses) may be responsible for the shift of the MPB. Consequently, the dielectric permittivity is significantly improved for this composition, showing the best ferroelectric response obtained up to now for films of the BNBT system (P r  = 13.0 μC/cm 2 , E c  = 70 kV/cm).