Electrical Conductivity and Dielectric Properties of Bi$_{4}$Ti$_{3}$O$_{12}$

Abstract

The present paper deals with the investigation of electrical and dielectric properties of structures based on Bi$_{4}$Ti$_{3}$O$_{12}$ films. It has been found that the nonlinearity of the $I - U$ characteristics in Me-Bi$_{4}$Ti$_{3}$O$_{12}$-Me structures is attributed to intercrystalline potential barriers. The height of the intercrystalline barrier ($\Phi_{0}=0.12$ eV) and the mean size of crystallise ($L=0.3~\mu$m) have been determined. At rather low temperatures, the hopping conductivity with a mean length of hopping, $\sim 2.6 \times 10^{19}$ cm$^{-3}$ eV$^{-1}$, is shown to be a dominant process at the charge transfer. It has been found that the electrical conductivity ($\sigma$) in the direction parallel to the $C$-axis (“sandwich” configuration) shows an anomaly in the phase transition region ($\sim 950$ K), while in the direction perpendicular to the $C$-axis, a simple bending of $\sigma$ vs. $T$ is observed. The latter is explained by the change of spontaneous polarization in Bi$_{4}$Ti$_{3}$O$_{12}$ films. The temperature dependence of the dielectric constant and the dielectric loss tangent have the maxima in the range of the phase transition temperature. The dielectric constant values are $\sim 650 \sim 120$ for the structures of “sandwich” and planar configurations, respectively. This fact indicates the presence of a polarization component in the given direction. The diffusion of the phase transition is explained by the imperfection of the film structure