%0 Journal Article
%T Conductivity and Complex Electrical Formalism of the Iron-Doped PbLaTiO3 Ferroelectric Relaxor
%A Lhaj Hachemi Omari
%A Salaheddine Sayouri
%J ISRN Materials Science
%D 2013
%R 10.1155/2013/231302
%X Polycrystalline perovskite nanomaterials (Pb0.88La0.12) O3 were prepared by sol-gel reaction method. The crystal structure examined by X-ray powder diffraction indicates that the material was single phase with pseudocubic structure. EDX and SEM studies were carried out in order to evaluate the quality and purity of the compounds. The crystal symmetry, space group, and unit cell dimensions were determined from Cell-Ref software, whereas crystallite size was estimated from Scherrer¡¯s formula. A correlation between grain size and diffuse character for the samples has been observed. Dielectric studies exhibit a diffuse phase transition characterized by a strong temperature and frequency dispersion of the permittivity and a relaxor behaviour. We have observed that dielectric constant decreases and ac conductivity increases with the frequency. The dielectric relaxation has been modeled using the Curie-Weiss and modified Curie-Weiss laws. The calculated activation energy for % and 3% was between 0.91¨C2.1£¿eV and 0.425¨C1.08£¿eV, respectively. The relaxation times were estimated from the Arrhenius law. 1. Introduction Perovskite-structured ferroelectric crystals have the general formula ABO3, where A is mono- or divalent ion with large radius and low valence, while B is a tetra- or pentavalent ion with small radius and high valence [1]. Among the perovskite-type oxides, titanate ceramics have been considered as interesting materials for room temperature applications, mainly due to their interesting dielectric properties [2]. Lead titanate (PbTiO3), with a very high Curie temperature of 490¡ãC, belongs to a most important perovskite family due to its remarkable ferroelectric and piezoelectric features in polycrystalline form [3]. The phase transition behavior in PbTiO3 single crystal is relatively simple; it exhibits a single transition from paraelectric with cubic phase to ferroelectric with tetragonal phase [4]. It has been observed that substitution of any suitable ions at the Pb and/or Ti site of lead titanate results in substantial modification in their electrical properties so as to make them suitable for a wide variety of industrial applications. The doping subsistent can either occupy A-site, B-site, or both, as a donor or an acceptor, based on chemical valence with respect to the original ions. The electrical properties of the ceramics are a result of different contributions from various components and processes in the materials. The charge transport can take place via modes, such as dipole reorientation, charge displacement, and space charge formalism [5].
%U http://www.hindawi.com/journals/isrn.materials.science/2013/231302/