<p>Cobalt-substituted calcium ferrites (CCAFs) with compositions Co_<i>x</i>Ca_1–<i>x</i>Fe₁₂O₁₉ (<i>x</i> = 0&#xa0;−&#xa0;0.25) were synthesized using the solution combustion method to examine their structural and electrical properties. X-ray diffraction confirmed the formation of a single-phase hexagonal magneto-plumbite structure, with crystallite dimensions decreasing from 45.19 to 34.75&#xa0;nm, indicating nanoscale grain growth following Cobalt substitution. FTIR spectra showed typical metal–oxygen stretching vibrations at tetrahedral and octahedral sites. This showed that Co²⁺ ions had been successfully added to the ferrite lattice. SEM tests revealed that the nano-grains were evenly distributed and had a porous structure, resulting in a large active surface area suitable for gas adsorption. Nanoscale ferrites provide improved sensitivity due to enhanced interaction between target gas molecules and surface oxygen species, which directly influences the change in electrical resistance during sensing. Dielectric analysis revealed a high dielectric constant and loss at low frequencies that decrease as the frequency increases. This agrees with Maxwell–Wagner interfacial polarization and the two-layer model of Koop’s, where conductive grains and resistive grain boundaries are responsible. The Verwey electron-hopping mechanism between Fe²⁺ and Fe³⁺ ions caused the AC conductivity to go up with frequency. Cobalt substitution made this even better. Complex impedance analysis revealed non-Debye relaxation behavior, with relaxation times spanning from 0.2 to 1.99&#xa0;μs. The materials also acted as semiconductors when the temperature went up. These combined structural, dielectric, and conduction properties demonstrate that CCAFs are suitable for chemical and gas-sensing applications that require stability, sensitivity, and affordability.</p>