Structural and electrical properties of Al3+ ions doped nanocrystalline Mg0.2Mn0.5Ni0.3AlyFe2-yO4 ferrites synthesized by citrate precursor method

Structural and electrical properties of nanocrystalline Mg0.2Mn0.5Ni0.3AlyFe2 O-y(4) (y = 0.0-0.30) cubic spinel ferrites prepared by the citrate precursor technique have been studied. The samples were characterized by X-ray diffraction technique at room temperature. The crystal size and lattice constant decreases with increase in aluminum concentration. The analyses of transmission electron microscopy (TEM) study show the crystal size variation within the range 6-12 nm. The dc-electrical resistivity decreases with increase in temperature exhibiting the semi-conductor like behavior. It was observed that dc-electrical resistivity and activation energy increases with increasing concentration of Al3+ ions which have been explained on the basis of Verwey's hopping mechanism. The dielectric constant (epsilon') and dielectric loss (epsilon '') have been studied as a function of frequency and temperature in the frequency range 0.075-30 MHz. The dielectric constant and dielectric loss decreases with increase in non magnetic Al3+ ions concentration. The dielectric constant of these ferrites is approximately inversely proportional to the square root of the dc-resistivity. The phenomenon of dispersion in the dielectric constant and dielectric loss show normal behavior with frequency which was attributed to Maxwell-Wagner type interfacial polarization in accordance with Koop's phenomenological theory. (C) 2013 Elsevier B. V. All rights reserved.