Auto-ignition synthesis of CoFe2O4 with Al3+ substitution for high frequency applications

A series of CoAlxFe2-xO4 (0 <= x <= 1.0) was synthesized by sol-gel auto combustion method using nitrates of respective elements and by keeping 1:3 ratio of metal nitrate to citrate. The resultant powders were investigated by various techniques. Fourier transform infrared spectroscopy (FT-IR) is employed to determine the local symmetry in crystalline solids and to shed light on the ordering phenomenon. The XRD revealed that the powders obtained are single phase with inverse spinel structure. Evaluation of TEM confirms fine particle nature of the particles. SEM analysis and EDAX indicate that the samples were homogeneous and had the expected Fe-Co-Al ratios. As aluminium content increases, the measured magnetic hysteresis curves become broader and the saturation magnetization decreased. Coercivity increased from 975 to 4191 Oe with Al3+ substitution. An increase in electrical resistivity, coercivity and dielectric characterization made present samples suitable for use in high frequency device applications.