Study of cation distribution for Cu-Co nanoferrites synthesized by the sol-gel method

摘要

Nano sized polycrystalline soft ferrite particles with composition Cu_(1-x)Co_xFe_2O_4 (x =0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by the sol-gel technique. The existence of well-defined single cubic spinel structure was confirmed in all the samples by X-ray diffraction. The crystallite size found by XRD varied from 14.8 to 34.0 nm. The microstructure was also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Slight expansion of the unit cell was detected with the increase of Cobalt concentration, which may be attributed due to larger ionic radius of Co~(2+). Lattice parameter ranged from 8.34 A to 8.37 A for Co~(2+) from 0.1-0.9. The distribution of cations amongst A- and B-sites of the lattice was estimated by X-ray diffraction by using the R-factor technique. The results showed that both Cu~(2+) and Co~(2+) ions occupy mainly the B-site while Fe~(3+) ions were equally distributed among A- and B-sites. The data obtained from cation distribution analysis was used to determine the magnetic moment for each sample and VSM studies were also carried out to validate these calculations. Magnetic measurements showed that the saturation magnetization (Ms) and coercivity (He) increased with increasing cobalt content.