Fuel additives and heat treatment effects on nanocrystalline zinc ferrite phase composition

Nanocrystalline ZnFe2O4 powder was prepared by the auto-combustion method using citric acid, acetic acid, carbamide and acrylic acid as fuel additives. Pure spinel zinc ferrite with the crystallite size of about 15 nm can be obtained by using acrylic acid as fuel additive. Samples prepared using other fuel additives contain ZnO impurities. In order to eliminate ZnO impurities, the sample prepared with citric acid as fuel additive was annealed at different temperatures up to 1000 °C in air and in argon. Annealed powders have pure ZnFe2O4 phase when annealing temperature is higher than 650 °C in air. Sample annealed at 650 °C in air is paramagnetic. However, annealed powders become a mixture of Fe3O4 and FeO after annealing at 1000 °C in argon atmosphere due to Zn volatility and the reduction reaction.

Research Highlights► The systematic study of the effects of different fuel additives on the structure of nanocrystalline zinc ferrite, which are used for the preparation of pure zinc ferrite. ► Study the effects of different annealing temperatures and atmospheres on the structure and magnetic properties of zinc ferrite. ► Analyze the structure and magnetic properties of zinc ferrite powder both theoretically and experimentally. ► The conclusions derived from the work for the preparation of high performance zinc ferrite are of great value.