A DTA and XRD study of the effect of Li 2 O doping on the solid-solid interaction between Fe 2 O 3 and ZnO showed that Fe 2 O 3 and ZnO interacted above 600°C to produce ZnFe 2 O 4 . The extent of ferrite formation increases with temperature, but not completely when pure mixed solids are pre-heated at 900°C. These results are attributed to the initially formed zinc ferrite layer inhibiting diffusion of Fe 2 O 3 and ZnO and thus acting as an energy barrier. Li 2 O doping (1.5 and 3 mol%) stimulated the formation of zinc ferrite to a degree that increased with the amount present. The mechanism of the promotion effect is discussed.