J. Phys. III France
Volume 6, Numéro 7, July 1996
Page(s) 853 - 861
DOI: 10.1051/jp3:1996159
J. Phys. III France 6 (1996) 853-861

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

A.A. Agasiev, M.Z. Mamedov and M.B. Muradov

Baku State University, Baku 370145, Azerbaijan

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

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 ( $\Phi_{0}=0.12$ 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 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 $\sim 650 \sim 120$ 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.

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