Hindawi Publishing Corporation ISRN Materials Science Volume 2013, Article ID 231302, 11 pages http://dx.doi.org/10.1155/2013/231302 Research Article Conductivity and Complex Electrical Formalism of the Iron-Doped PbLaTiO 3 Ferroelectric Relaxor Lhaj Hachemi Omari and Salaheddine Sayouri Laboratoire de Physique T´ eorique et Appliqu´ ee, D´ epartement de Physique, Facult´ e des Sciences-DM, 30 000 F` es, Morocco Correspondence should be addressed to Salaheddine Sayouri; ssayouri@yahoo.com Received 17 December 2012; Accepted 29 January 2013 Academic Editors: D. Chicot, M. Martino, A. O. Neto, D. Sands, and H. Zhang Copyright © 2013 L. H. Omari and S. Sayouri. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Polycrystalline perovskite nanomaterials (Pb 0.88 La 0.12 )(Fe  Ti 1− ) 0.97 O 3 were prepared by sol-gel reaction method. Te crystal structure examined by X-ray powder difraction 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. Te crystal symmetry, space group, and unit cell dimensions were determined from Cell-Ref sofware, whereas crystallite size was estimated from Scherrer’s formula. A correlation between grain size and difuse character for the samples has been observed. Dielectric studies exhibit a difuse 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. Te dielectric relaxation has been modeled using the Curie-Weiss and modifed Curie-Weiss laws. Te calculated activation energy   for =1% and 3% was between 0.91–2.1 eV and 0.425–1.08 eV, respectively. Te relaxation times were estimated from the Arrhenius law. 1. Introduction Perovskite-structured ferroelectric crystals have the general formula ABO 3 , 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 inter- esting materials for room temperature applications, mainly due to their interesting dielectric properties [2]. Lead titanate (PbTiO 3 ), with a very high Curie temperature of 490 ∘ C, belongs to a most important perovskite family due to its remarkable ferroelectric and piezoelectric features in poly- crystalline form [3]. Te phase transition behavior in PbTiO 3 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 modifcation in their electrical properties so as to make them suitable for a wide variety of industrial applications. Te 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. Te electrical prop- erties of the ceramics are a result of diferent contributions from various components and processes in the materials. Te charge transport can take place via modes, such as dipole reorientation, charge displacement, and space charge formalism [5]. It is wellknown that transition ions, having partially flled d-orbital like Mn 3+ , Fe 3+ ions, are generally used at B-site. Fluctuation of the oxidation state of these ions results in the formation of oxygen ion vacancies which causes thermally activated conduction. Tus, most of the multiferroic materials show high leakage current and low ferroelectric polarization [6]. In order to improve the ferro- electric properties, lanthanum (La) has been introduced. An appropriate and optimum amount of La lowers the leakage current and provides good bistable polarization, which is a primary requirement for nonvolatile random access memory (NVRAM) applications [7]. Sol-gel process has been used to synthesize nanocrys- talline ferroelectrics. Tis method ofers several advantages (such as gaining time, saving energy, and better homogeneity) more than the other conventional methods. It was shown