In this study, powders of nickel—cadmium ferrites are synthesised using sol—gel technology and autocombustion (SGA method). After completing the process of autocombustion, a single-phase NiFe$_{2}$O$_{4}$ powder is obtained with a spinel cubic structure of space group $Fd3m$. In the ferrite powders, containing substituting nonmagnetic ions, additional phases of the NiO, CdO and $\alpha$-Fe$_{2}$O$_{3}$ oxides are also enclosed. After burning at a temperature of 900°C for 3 hours, the monophase powders are obtained. The average size of coherent scattering regions of monophase powders is found to be in the range of 42—61 nm. As shown, the lattice parameter increases with increasing content of Cd$^{2+}$ ions. The optical properties of ferrite powders are studied depending on the degree of substitution of nickel ions with the cadmium ones. As a result of analysis of the absorption spectra, it is revealed that, for all investigated powders, the allowed direct transition of electrons from the valence band to the conduction band is inherent. As shown, the optical band gap increases with increasing concentration of cadmium ions in the ferrite structure, and it is in the range of 1.91 to 2.56 eV.