FTIR Studies and Dielectric Properties of Cr Substituted Cobalt Nano Ferrites Synthesized by Citrate-Gel Method

Nanoparticles of Co CrxFe2-xO4 with stoichio metric proportion x =0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 were prepared by the Citrate-gel auto co mbustion method. The samp les were sintered at 500℃ for 4h in air. Structural characterizat ion of sintered samples was carried out by X-ray diffraction and Fourier Transform infra-red spectroscopy (FTIR). X-ray diffract ion studies of all the Ch ro miu m substituted Cobalt nano ferrites showed a homogeneous single phased cubic spinel with a crystallite size of the part icles in the range of 6-12n m. FTIR spectra of samples under investigations reveal the format ion of a single phase cubic spinel, showing two significant absorption bands. The high frequency band (ν1) around 600 cm -1 is attributed to the intrinsic vibrations of tetrahedral comp lexes and the low frequency band (ν2) around 400 cm -1 is due to octahedral co mp lexes. The dielectric parameters such as dielectric constant (real and imaginary parts-e' and e"), loss tangent (tan δ) and AC conductivity( σAC) for all the samples were studied as a function of frequency in the range of 20Hz to 2MHz at roo m temperature using Agilent E4980A Precesion LCR meter. The dielectric constant, loss tangent and AC conductivity shows a normal dielectric behavior with frequency which reveals that the dispersion is due to the Maxwell-Wagner type interfacial polarization in general and hopping of charge between Fe 2+ and Fe 3+ . A qulitative explanation is given for co mposition and frequency dependance of the dielectric constnat, dielectric loss tangent and AC conductivity of the nano ferrite. A relaxat ion peak was observed in the loss tangent property of nano ferrite samp le with composition Co Cr0.1Fe1.9O4. The loss tangent for the synthesized samples was found to be decreased from 0.062 to 0.055 in higher frequency region showing the potential applications of these materials in h igh frequency micro wave devices. On the basis of these results the explanation of dielectric mechanis m in Co-Cr nano ferrites is suggested.