Study of dielectric and ac impedance properties of Ti doped Mn ferrites

We have reported dielectric and ac impedance properties of Ti doped Mn1+xFe2-2xO4 (0 <= x <= 0.5) ferrites prepared by solid-state reaction method, using dielectric and impedance spectroscopy in the frequency range of 42 Hz-5 MHz, between the temperatures (300K-473K). The dielectric constant and dielectric loss (tan delta) decreases with increasing frequency but these parameters increase with increasing temperature. The dielectric loss tangent curves exhibit dielectric relaxation peaks at high frequencies (3.6 kHz-5 MHz), which are attributed to the coincidence of the frequency of charge hopping between the localized charge states and the external field. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell-Wagner's two-layer model and the hopping of charge between Fe2+ and Fe3+ as well as between Mn3+ and Mn2+ ions at B-sites. The complex impedance analysis has been used to separate grain and grain boundary in Studied samples. Two semicircles corresponding to grain and grain boundary have been observed at low temperature, while only one semicircle has been seen at high temperatures. The resistance of grain and grain boundary both increase with Ti4+ doping. (c) 2009 Elsevier B.V. All rights reserved.