Les effets des phases du dioxyde de Titane sur les propriétés structurales et diélectriques des céramiques du type BaTiO3 + x % mole Fe2O3.

Abstract

The objective of this investigation is to study the influence of TiO2 phases on the structural and dielectric properties of the BaTiO3 ceramics containing different amounts of Fe2O3. The pure BaTiO3 ceramics was prepared by a solid state reaction between BaCO3 and both of TiO2 phases ; anatase (A) and rutile (R), respectively. We prepared the mixtures by stoichiometric way, which were calcined at 1100 °C during 2hours. The formations of perovskites structures ABO3 were confirmed by X rays diffraction analysis. While the ceramics mixture with (1-x) BaTiO3+ x % Fe2O3 (where x = 1, 2, 5 and 7 wt %) compositions were prepared by the wet milling. Afterwards, the different pellets were fabricated by uniaxial compression and sintered at different temperatures (1300, 1350 and 1400 °C). The obtained results show an increase in the tetragonality due to the doping by Fe3+, consequencely an increase in the relative permittivity of samples prepared from TiO2(R) with both of Fe2O3 addition and sintering temperature. On the other hand, for the samples prepared from TiO2 (A) the obtained results show a decrease in both relative density and tetragonality with both of Fe2O3 addition and sintering temperature, as a consequence we get a decrease in the relative permittivity compared with pure BTA. The Curie-Weiss law shows a linear ferroelectric property for Fe doped both BTA and BTR ceramics with a first order type of Curie phase transition. In other hand, the modified Curie-Weiss law shows a partially relaxor ferroelectric behavior for both Fe-doped BTA and BTR ceramics. The electrical resistivity evolution in term of temperature shows a semiconductor behavior with independence between applied potential and activation energy, where Fe3+ ions act as an acceptor