Microstructure and ferroelectric properties of compositionally graded Nd-doped Bi 4 Ti 3 O 12 thin films prepared by sol–gel method

The compositionally graded Bi 4−x Nd x Ti 3 O 12 (BNT) thin films were prepared on Pt/Ti/SiO 2 /Si substrates by sol–gel method. Their microstructure, ferroelectric and dielectric properties were investigated. The single-phase upgraded and downgraded BNT films were obtained with (117) preferred orientation. Compared to the homogeneous BNT films prepared by the same conditions, the remanent polarization ( P r ) and permittivity ( ε r ) of compositionally graded BNT films were significantly enhanced. The upgraded BNT film showed larger 2 P r (34.9 μC/cm 2 ) and ε r (509), and those of downgraded BNT film were 29.4 μC/cm 2 and 505. Bi element in the downgraded BNT film accumulated near the interface of film/Pt bottom electrode, which deteriorated the compositional gradient and resulted in decreasing 2 P r and ε r compared to the upgraded BNT film.