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J Mater Sci: Mater Electron (2011) 22:426429 DOI 10.1007/s10854-010-0154-3
Dielectric relaxation phenomena in the compound: LiCo3/5Mn1/5Cu1/5VO4
Moti Ram
Received: 5 March 2010 / Accepted: 25 June 2010 / Published online: 8 July 2010 Springer Science+Business Media, LLC 2010
Abstract Solution-based chemical method has been used to produce LiCo3/5Mn1/5Cu1/5VO4 ceramics. The formation
of the compound is checked by X-ray diffraction analysis and it reveals an orthorhombic unit cell structure with lattice parameters of a = 9.8262, b = 3.0706, c =14.0789. Field emission scanning electron micrograph indicates a polycrystalline texture of the material with grains of unequal sizes (*0.2 to 3 lm). Complex impedance spectroscopy technique is used to study the dielectric properties. Temperature dependence of dielectric constant (er) at various frequencies exhibits the dielectric anomalies in er at Tc (transition temperature) = 245, 255, 260 and 265 C with (er)max. *458, 311, 214 and 139 for 50, 100, 200 and 500 kHz, respectively. Frequency dependence of tangent loss at various temperatures shows the presence of dielectric relaxation in the material.
1 Introduction
In recent years, the synthesis and sintering of ceramic oxide materials have become an important part of modern ceramic research due to their technological applications [1]. One family of such oxides is spinel oxides having general formula AB2O4, where cations A occupy one-eighth of the tetrahedral sites in a face-centered cubic close packed oxygen sublattice and cations B occupy half of the octahedral sites [2]. One such oxide is LiCo3/5Mn1/5Cu1/5VO4,
which is mechanically strong. Dielectric properties of such oxides are sensitive to the applied electric eld frequency,
preparation conditions, chemical compositions and doping of additives [3]. The measurement of frequency dependence of dielectric properties can reveal dielectric relaxation associated with local motions (reorientations, ion jumps) [4, 5]. It depends on either intrinsic or extrinsic heterogeneities due to special heat treatments (quenching, annealing, etc.), ionic substitutions, grain size additives, and grain boundary nature [4, 6]. The frequency dependence of dielectric properties of these materials has successfully been studied using complex impedance spectroscopy methods [7]. This technique resolves the contributions and relative importance to electrical conduction and/or polarization of different phenomena in the studied frequency region. The purpose of the present work is to study the structural and dielectric properties (dielectric constant, tangent loss...