Effect of d-block element Co2+ substitution on structural, Mössbauer and dielectric properties of spinel copper ferrites

The present work focuses on the influence of replacement of d-block element Cu2+ ion by Co2+ in Cu-spinel ferrites [Cu1−xCoxFe2O4 (x = 0.0, 0.1, 0.2, 0.4, 0.6, and 1.0)] on the structural, vibrational and dielectric properties as synthesized by Solid-state reaction route. A structural transition from tetragonal (space group I41/amd)) to cubic (space group Fd3m) phase is observed due to introduction of cobalt. Cubic spinel- type structure at room temperature of Cu1−xCoxFe2O4 (0.4 ≤ x ≤ 1.0) is confirmed by Rietveld - refined X-ray powder diffraction patterns. Raman spectroscopic studies reveal 2 (5) optical active modes in CuFe2O4 (CoFe2O4) at room temperature. Transmission Mössbauer spectroscopy of Cu1−xCoxFe2O4 (x = 0.0, 0.2 and 0.6) shows two sets of six-line hyperfine patterns for all the three samples, indicating the presence of Fe in both A and B sites. Identification of sites is accomplished by evidence from hyperfine distribution and isomer-shift data. Dielectric constant and dielectric loss tangent measured in the frequency range from 1 KHz to 1 MHz at room temperature are found to be decreasing with the increase in frequency.