Mecanosynthesis of partially inverted zinc ferrite

Abstract

Synthesis of zinc ferrite (ZnFe 2O 4) by high-energy ball-milling from a powder mixture of zinc oxide (ZnO) and hematite (α-Fe 2O 3) is investigated. The millings are performed under air using tungsten carbide vials and balls. The spinel phase appears within 2 h grinding and the reaction is almost complete after 24 h. The broadening of X-ray diffraction lines shows that the crystallite size is around 10 nm. Mössbauer spectra indicate that there is some inversion in the ferrite, leading to the formula (Zn 0.31 2+Fe 0.69 3+) A(Zn 0.69 2+Fe 1.31 3+) BO 4 2− for the 24 h sample. We also show that preliminary millings of the initial oxides (zincite and hematite) slow down the reaction. Finally, dilatometric studies show that the shrinkage proceeds in several steps, due to a grain size distribution in the sample.