Structural and microwave characterization of Ni0.2CoxZn0.8−xFe2O4 for antenna applications

Nickel–cobalt–zinc ferrites, Ni0.2CoxZn0.8−xFe2O4 (with x=0, 0.2, 0.4, 0.6, 0.8,) have been prepared using the auto-combustion method. X-ray diffraction, Fourier transform infrared (FT-IR) and Raman spectroscopy confirmed the cubic spinel structure of the ferrites. Microwave dielectric constant (εr) and quality factor (Q×f) were measured by using the Hakki–Coleman technique. Dielectric constant calculated using the Clausius–Mossoitti relation showed good agreement with the experimental value. Relative permeability of the ferrites was calculated by using the Nicholson–Ross–Weir conversion technique. Dielectric constant (εr) decreased from 7.474 to 5.548 and temperature coefficient of resonant frequency (τf) increased from −75.85 ppm/°C to −19.32 ppm/°C, respectively, and relative permeability increased from 2.1085 to 3.2179 with increase in Cobalt content. The composition Ni0.2Co0.2Zn0.6Fe2O4 was used to develop ferrite resonator antennas (FRA) and was studied in cylindrical, triangular and cuboid shapes with co-axial probe feeding mechanisms. The antenna characteristics were simulated using high frequency structure simulation (HFSS) software and a good agreement has been achieved between the measured and simulated results. The cuboid shaped FRA show maximum bandwidth of 990 MHz, while the cylindrical shaped FRA show a maximum gain of 3.48 dB, respectively.