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 νA and octahedral νB were observed around 575 cm−1 and 400 cm−1, respectively. It was found the threshold frequency νth for the electronic transition increases with increasing the Ge content. The Debyeʹs temperature θD was calculated and it was found dependent on the type of charge carriers. AC conductivity σac with dielectric properties (dielectric constant ɛ′, dielectric loss ɛ″ and loss tangent tan δ) as a function of frequency (f = 102 → 106 Hz) at room temperature have been measured. The dispersion of the dielectric properties was discussed in the light of Koopʹs phenomenological theory. The phonon frequency νph 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 104–105 Hz.