Structural, magnetic, and electrical properties of Ni0.38−xCu0.15+yZn0.47+x−yFe2O4 synthesized by sol–gel auto-combustion technique

Various polycrystalline compositions Ni 0.38− x Cu 0.15+ y Zn 0.47+ x − y Fe 2 O 4 [( x , y ) = (0.00, 0.01)] are prepared through the sol–gel auto-combustion technique and sintered at 850, 950, 1050, and 1150 °C for 5 h in air. The single-phase cubic spinel structures of the compositions are confirmed by X-ray diffraction analysis. No secondary phases are observed in the X-ray diffraction patterns. The lattice constant is found to increase with doping of Zn 2+ in place of Ni 2+ and decrease with doping of Cu 2+ in place of Ni 2+ . The bulk density of ferrites increases with sintering temperature up to 1050 °C, then decreases. The field emission scanning electron microscopy is used to demonstrate the surface morphology of the materials. The maximum grain size (1.97 µm) is found for the composition Ni 0.38 Cu 0.16 Zn 0.46 Fe 2 O 4 . The maximum bulk density (4.42 × 10 3 kg/m 3 ), maximum initial permeability, and highest relative quality factor (≥ 6000) are observed for the composition Ni 0.38 Cu 0.16 Zn 0.46 Fe 2 O 4 sintered at 1050 °C. The values of dielectric constants, impedance, and AC resistivity are found higher at lower frequencies but become almost constant at higher frequencies, which can be explained based on the hopping mechanism. The investigated ferrites exhibit comparatively higher permeability, lower eddy current loss, and higher resistivity, which make them suitable for wireless power transfer (WPT) applications.