IR spectra and dielectric properties of Cu-Ge ferrite

The mixed ferrite Cu1+xGexFe2-2xO4; where x = 0.0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3; was prepared from high purity oxides using the standard ceramic technique. The IR spectra were recorded on the range from 200 to 1000 cm(-1). The two primary bands corresponding to tetrahedral nu(A) and octahedral nu(B) were observed around 575 cm-1 and 400 cm(-1), respectively. It was found the threshold frequency nu(th), for the electronic transition increases with increasing the Ge content. The Debye's temperature theta(D) was calculated and it was found dependent on the type of charge carriers. AC conductivity sigma(ac), with dielectric properties (dielectric constant epsilon', dielectric loss epsilon `' and loss tangent tan delta)as a function of frequency (f = 10(2) -> 10(6) Hz) at room temperature have been measured. The dispersion of the dielectric properties was discussed in the light of Koop's phenomenological theory. The phonon frequency nu(ph) which calculated from IR spectra for each composition of Cu-Ge ferrite was found to be higher than that calculated from the AC conductivity by a factor of about 10(4)-10(5) Hz. (C) 2011 Elsevier B.V. All rights reserved.