Known as a hard magnetic material, cobalt ferrite belongs to one of the most attractive classes of materials owing to its diverse technical applicability such as in catalysis, sensors, batteries. In this study, we synthesized Li- and Y-substituted cobalt ferrite nanoparticles using a sol–gel combustion method. Their mean crystallite sizes with spinel structures were calculated as 15–19 and 2–5 nm and their lattice constant values were 7.8 ± 0.02 and 8.5 ± 0.3 Å, respectively. The results also revealed that the band gap energy values of the prepared Li- and Y-doped cobalt ferrites decreased after doping compared with that of pure cobalt ferrite, and thus they appear to be promising for energy generation and storage applications. © 2018, Indian Association for the Cultivation of Science.