Influence of La3+ substitutions on structural, dielectric and electrical properties of spinel cobalt ferrite

Abstract

La3+ doped cobalt ferrites with composition CoLaxFe2−xO4 (0.00 ≤ x ≤ 0.20) were synthesized by a co-precipitation method. X-ray diffraction (XRD) analysis confirm the formation of single-phased spinel structure for all synthesized samples. The result of La3+ doping on dielectric and electrical properties of cobalt ferrites was investigated. Dielectric constant and dielectric loss decrease with increasing frequency whereas alternating current (AC) electrical conductivity increases with increasing frequency. The AC electrical conductivities were effectively modeled by employing the Jonscher’s power law. Role of grain and grain boundary on impedance has been explored from nyquist plots and equivalent electrical circuits were proposed to clarify the impedance spectroscopy results. The Direct Current (DC) electrical resistivities were estimated by two probe method within the temperature range of 303K–700K. DC electrical resistivity decreases with increasing temperature and explained by hopping mechanism. DC electrical resistivity and drift mobility decreases with La3+ doping. Activation energies were calculated by employing the Arrhenius plot. Activation energy found to increases with La3+ substitutions. Maximum value of DC electrical resistivity achieved was 9.26 x 10+8 (Ω-cm) with crystallite size 17 nm. Current-Voltage (I–V) measurements were carried out within 0→6V→0V→ –6V→0V voltage range. It is worth mentioning that all doped sample exhibited remarkable and improved nonlinear hysteresis loop-type behavior than pour sample. Variation in resistance, in current-voltage loops, is clarified by considering space charge limited conduction (SCLC) model and oxygen vacancies migration across the metal-semiconductor interface. Out study suggest that La3+ doped cobalt ferrites may be tested as an active material for possible applications in non-volatile memory devices and neuromorphic applications.