Microstructure and ferroelectric properties of compositionally graded Nd-doped Bi4Ti3O12 thin films prepared by sol-gel method

The compositionally graded Bi4-xNdxTi3O12 (BNT) thin films were prepared on Pt/Ti/SiO2/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 (epsilon (r)) of compositionally graded BNT films were significantly enhanced. The upgraded BNT film showed larger 2P (r) (34.9 mu C/cm(2)) and epsilon (r) (509), and those of downgraded BNT film were 29.4 mu C/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 2P (r) and epsilon (r) compared to the upgraded BNT film.