Electrical Conductivity and Dielectric Properties of Bi ₄Ti ₃O ₁₂

(Received 19 June 1995, revised 15 January and 15 April 1996, accepted 17 April 1996)

Abstract
The present paper deals with the investigation of electrical and dielectric properties of structures based on Bi ₄Ti ₃O ₁₂ films. It has been found that the nonlinearity of the I - U characteristics in Me-Bi ₄Ti ₃O ₁₂-Me structures is attributed to intercrystalline potential barriers. The height of the intercrystalline barrier (  eV) and the mean size of crystallise ( m) have been determined. At rather low temperatures, the hopping conductivity with a mean length of hopping,  cm ^-3 eV ^-1, is shown to be a dominant process at the charge transfer. It has been found that the electrical conductivity ( ) in the direction parallel to the C-axis ("sandwich" configuration) shows an anomaly in the phase transition region (  K), while in the direction perpendicular to the C-axis, a simple bending of vs. T is observed. The latter is explained by the change of spontaneous polarization in Bi ₄Ti ₃O 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 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.