Electrical properties of Fe-doped BaTiO3

Abstract

The polymorphism of BaTi_1−xFe_xO_3−δ solid solutions: 0 < x < 0.1, prepared by a sol–gel method, has been determined and presented in the form of a temperature–composition phase diagram for T > ∼1000 °C. With increasing x, the high temperature hexagonal polymorph is stabilised to increasingly lower temperatures. The temperature of the tetragonal to cubic transition also decreases with increasing x, as shown by a combination of permittivity measurements, DSC and X-ray powder diffraction. The electrical properties of ceramics of tetragonal/cubic solid solutions, determined by impedance spectroscopy, show a ferroelectric bulk phase (for T < T_c) and a Schottky barrier associated with the grain boundaries whose resistance is sensitive to a dc bias voltage. The bulk properties are sensitive to sample heat treatment and in particular, for samples reheated in air ≤700 °C, oxidation occurs, generating Fe⁴⁺ and an increase in the level of p-type conductivity.