Infra-red absorption and dielectric properties of Li-Cu ferrite

The mixed ferrites Li0.5-0.5xCUxFe2.5-0.(5x) (where x = 0 to 1) were prepared by the ceramic method. infra-red (IR) absorption and dielectric properties were used to investigate this ferrite. The IR spectra in the range from 200 to 1000 cm(-1) were reported. Mainly, two bands were observed. The band at around 575 cm(-1) (v(1){*}) and the band at around 385 cm(-1) (v(2){*}) were assigned to the tetrahedral and octahedral complexes, respectively. A small band at about 325 cm(-1) (v(3)) indicated the presence of octahedral divelant metal-oxygen in complexes. This band decreases with the increase of copper concentration and completely disappears at sample of x greater than or equal to 0.3. The threshold frequency for the electronic transition was determined. It was found that the threshold frequency for electronic transition seems to be decreasing with increasing Cu2+ content. The ac conductivity <(sigma)over tilde> and dielectric properties (dielectric constant epsilon', dielectric loss epsilon `` and loss tangent tan delta) were measured at room temperature as a function of frequencies from 10(2) to 10(6) Hz. A hopping model was applied in order to discuss the obtained results. The frequency exponential factor s, was estimated and compared with available data.