Synthesis and magnetic properties of ZnFe2O4 obtained by mechanochemically assisted low-temperature annealing of mixtures of Zn and Fe oxalates

The mechanism of formation of zinc ferrite (ZnFe₂O₄) from ZnC₂O₄·1.8H₂O-2Fe^IIC₂O₄·2H₂O and ZnC₂O₄·1.8H₂O-Fe₂^III(C₂O₄)₃·6H₂O mixtures is investigated. By combination of TG and XRPD measurements it has been shown that microcrystalline ZnFe₂O₄ forms from physical mixtures after prolonged annealing at 1000 °C while nanocrystalline ZnFe₂O₄ powders are produced by mild annealing (1 h at 500 °C in air) of mechanically activated mixtures. The magnetic properties of ZnFe₂O₄ powders obtained from physical and from milled mixtures are compared.