Comportamento relaxador da hexaferrita de bário modificadas com íons de La 3+ e Al 3+

Abstract

The Ba 0.9 La 0.1 F e 12−y O 19 hexaferrites modified with Al 3+ and La 3+ were synthesized by the conventional ceramic method. At room temperature Rietveld refinement and X-ray diffraction confirmed the formation of type M hexaferrite structure. The behavior of electrical properties; Impedance, permittivity, electrical modulus and conductivity were analyzed through the dielectric relaxation model obtained by the impedance spectroscopy technique. The parameters of relaxation; Relaxation time and correlation parameters are obtained using the fitting of the electrical module curves and conductivity using the Havrialiak-Negami model and Dyre random domain model, respectively. Comparison of these parameters are made by frequency and time domain analysis. The results indicate the appearance of a dipolar relaxation process in pure barium hexaferrite, and an interfacial relaxation process due to the accumulation of charge carriers at the interface between grain and Maxwell-Wagner-Sillar grain contours in barium hexaferrite. modified with La 3+ ions at concentrations of 0.1 and 0.6 at room temperature. In the case of the ceramic system Ba 0.9 La 0.1 F e 12−y O 19 appears only the process of interfacial relaxation at room temperature. The relaxation peak as well as the parameters depend on the concentration of the Al 3+ ions. Conductivity increases for lower concentrations, less than 0.6 of Al 3+ , for values between 0.6 and 0.8 conductivity decreases, and for concentrations greater than 0.8 conductivity is close to that obtained for ceramics BaM La 0.1 . The Dyre model presents a good fit on conductivity behavior, with mean square deviation value greater than 0.99, when there is electron hopping conductivity. In all cases there is an increase in conductivity with respect to pure hexaferrite which indicates the potential of these systems as electromagnetic radiation absorbers. Hexaferrites are targeted by research due to their multiferroic properties and as absorbing materials for electromagnetic radiation in the microwave range, research currently developed in our group.