The effects of calcination temperature, molar ratio and Li 2O doping on the interaction between ferric and nickel oxides were investigated using TG, DTA, dDTA and XRD techniques. The results obtained revealed that NiO retarded the crystallization of ferric oxide into the alpha phase and interacted with it to yield a well crystallized NiFe 2O 4 (trevorite) at temperatures starting from 700°C. However, the solid-solid interaction that gives rise to nickel ferrite was found to be affected by the molar ratio of NiO and Fe 2O 3 present. The complete transformation of the reacted oxides into the ferrite phase required prolonged heating at temperatures above 1100°C. Lithium oxide doping at 700 and 800°C modified the formation of nickel ferrite; the presence of 0.75 or 1.5 mol% of Li 2O depressed the ferrite formation, which was, however, enhanced in the presence of 3 mol% of Li 2O. Heating of the mixed solids doped with 1.5 mol% Li 2O at 800°C led to the formation of β-LiFeO 2, which was converted into α- and/or β-LiFe 5O 8 by increasing the amount of Li 2O to 3 mol%. The effect of Li 2O in modifying the solid-solid interactions between NiO and Fe 2O 3 and the formation of β-LiFe 5O 8 is discussed in the light of the dissolution of a portion of Li 2O and an increase in the mobility of Ni 2+ ions in the nickel oxide lattice.