Studies on the formation of zinc ferrite

Abstract

The reactions of zinc oxide with α-Fe₂O₃ and with γ-Fe₂O₃ leading to the formation of zinc ferrite (ZnFe₂O₄) have been studied at different partial pressures of oxygen in the temperature range 500-800°C. The ferrite spinel is formed more readily when γ-Fe₂O₃ is used as the reactant. The DTA and X-ray diffraction results indicate that the γ-Fe₂O₃ phase is stabilized in presence of ZnO. The lowering of partial pressure of oxygen in the ambient atmosphere favours the formation of zinc ferrite, indicating a cyclic redox process featuring Fe³⁺, Fe²⁺ and oxygen at the phase boundaries. At very low oxygen pressures, conversion to zinc ferrite is not facilitated, apparently due to the formation of an intermediate species, Fe_3-xZn_xO₄, which, under these conditions, is not easily converted to ZnFe₂O₄.