Microstructure and ferroelectric properties of Nb-doped Bi4Ti3O12 thin films prepared by sol-gel method

The effects of Nb doping on the ferroelectric properties of Bi4Ti3O12 (BIT) thin films were investigated. Ferroelectric Nb-doped Bi4Ti3O12 (BTN) thin films were prepared by a sol-gel spin-coating method and annealed at several temperatures in an oxygen atmosphere. From analyzing X-ray diffraction patterns, it could be determined that a randomly oriented film was obtained by doping Nb ion into BIT thin film. The BTN film consisted of more disordered plate-like grains whereas the plate-like grains in the BIT film were more parallel to the substrate. The remanent polarization (2Pr) and coercive field (2Ec) of the BTN thin film that annealed at 700 °C were about 39.8 μC/cm2 and 136.7 kV/cm at a sweep electric field of 175 kV/cm. The pulse polarization (Psw−Pns) and the shape of the hysteresis loops did not change significantly before and after the 1.5×1010 switching cycles.