Effect of Cd2+ substitution on some physical and chemical properties of nano-size Lithium-Nickel Ferrites

Ferrite materials are promising for addressing the global energy crisis and application in high-energy storage devices. For this, cadmium-substituted lithium ferrite Li0.4-x/2Ni0.2CdxFe2.4-x/2O4 (where x = 0.6, 0.7) was synthesized by the sol–gel auto-combustion method. X-ray diffraction (XRD) has been employed to confirm the crystal structure of spinel ferrites. Impurities detected in the XRD graph may be CdO formation; the XRD pattern confirms cubic spinel structure and the lattice parameter increased from 8.46 Å to 8.47 Å. The FESEM micrograph of the prepared sample pellets reveals particle diffusion due to non-uniform size. The grain sizes calculated from the FESEM micrographs are shown in the histogram as 186 nm and 153 nm, respectively. The larger grain size is attributed to the suppression of nanoparticles into large clusters, resulting in a spherical, large-stone like morphology. The saturation magnetization (Ms) was studied as a function of non-magnetic Cd substitution. Magnetic characteristics, including saturation magnetization (Ms), found at 32.61 emu/g and 21.42 emu/g and coercivity (Hc) was found at 103.83 emu/g to 51.54 emu/g, have decreased with an increase in cd content, as calculated from the M-H loop using a vibrating sample magnetometer (VSM). The electrochemical studies of fabricated electrodes were investigated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 m KOH electrolyte. The highest specific capacitance is 0.094 F/g for x = 0.6 and the scan rate of 5 mV/s, which has a good agreement for small-scale portable electronics devices. CV results show that with the increase in scan rate, specific capacitance decreases, and the area of the loop increases. CV measurements of the given ferrites indicate improved specific capacitance at a low scan rate. Electrochemical impedance spectroscopy shows a fast ion transfer reaction in the graph by a small semicircle and the straight line represents Warburg diffusion which can be a promising material for futuristic energy storage devices.