Solid–solid interactions between ZnO and Fe2O3 as influenced by Al2O3-doping

The solid–solid interactions between pure and alumina-doped zinc and ferric oxides have been investigated by using XRD technique. The investigated solids were calcined at 600–900°C. The amounts of alumina were 3, 6 and 9 mol%. The results obtained showed that Fe2O3 interacted readily with ZnO at temperatures starting from 700°C producing zinc ferrite. The degree of reaction propagation increased with temperature. The completion of this reaction required a prolonged heating at temperatures >900°C. Al2O3-doping promoted the ferrite formation to an extent proportional to its amount added. Furthermore, the doping process resulted in the formation of ZnFe2O4 at 600°C. The stimulation effect of Al2O3 was evidenced by following up the change of peak heights of certain diffraction lines characteristic for ZnFe2O4, α-Fe2O3 and ZnO phases located at “d” spacings of 2.54, 2.69 and 2.47 Å, respectively. The activation energies ΔE of the ferrite formation for pure and variously doped mixed oxide solids were computed. The ΔE values were 73.5, 66.8, 57.3 and 68.8 kJ mol−1 for pure mixed oxide solid samples and those doped with 3, 6 and 9 mol% Al2O3, respectively. The mechanism of Al2O3 doping is discussed.