Mechanism of dielectric nonlinear characteristics in bismuth-based cubic pyrochlores

A modified model is proposed to describe the dielectric nonlinear behavior in bismuth-based cubic pyrochlores by introducing non-tunable factor into Tagantsev׳s model. To validate the model, Bi1.5MgNb1.5−xTixO7 (BMNT) films were fabricated via chemical solution deposition. Bias field dependence of the permittivity predicted by the modified model agrees well with experimental results. A method for calculating barrier heights for hopping ions is presented based on the modified model. The maximum barrier heights for hopping dipoles in BMNT films derived from the model decrease from 0.206 eV to 0.172 eV with increasing Ti content from x=0 to x=0.15.