Spectroscopic and electrical properties of Mg-Ti ferrite doped with different rare-earth elements

The dielectric constant (epsilon'), and the electric conductivity (sigma) for Mg1+xTixRyFe2-2x-yO4, 0.025 <= y <= 0.15 doped with different rare-earth ions, R = Er, Cc and Nd were measured in the temperature range 300-750 K. The measurements were carried out as a function of frequency 50-1000 kHz X-ray diffractograms and IR spectra revealed that all the investigated samples posses the spinel structure. More than one conduction mechanism is used to interpret the electrical measurements. The most predominant one is the hopping mechanism that occurs between the ions of different valences existing on the same and different sites. All the ionic radii of the rare-earth used are too large to occupy the octahedral site. They form secondary phases on the grain boundaries. The electrical properties show that the pure sample has a larger dielectric constant as well as a larger valence exchange with respect to any doped one. This means that introducing rare-earth ions into the samples decreases epsilon' and increases the resistivity, owing to the decreasing Fe-Fe interaction. This feature can help to obtain well applicable ferrites. (c) 2006 Elsevier B.V. All rights reserved.