<p>Substituting ions with large ionic radii in spinel ferrites can significantly affect their physical properties. Co_1-<i>x</i>Ba_<i>x</i>Fe₂O₄ (<i>x</i> = 0.00, 0.10, 0.20, 0.30, 0.40, 0.50) ferrites prepared using the sol-gel citrate-nitrate method were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. All these techniques show the successful formation of the cubic spinel structure. The magnetic hysteresis loops measured by a vibrating sample magnetometer show that the saturation magnetization of the samples decreases from 53.8 to 39.6 emu/g with Ba substitution, while the coercivity shows an increasing trend from 640 to 1805 Oe. The electrical impedance analysis of the samples shows that the increased distortion and greater accumulation of grain boundaries (decrease in particle size) caused by barium substitution in Co_1-<i>x</i>Ba_<i>x</i>Fe₂O₄ ferrite leads to lower-frequency shifts in both <i>Z</i>” and <i>M</i>” spectra, which explains the increase in relaxation time and decrease in dielectric constant and conductivity.</p> Graphical Abstract <p></p>