Mecanosynthesis of partially inverted zinc ferrite

Synthesis of zinc ferrite (ZnFe(2)O(4)) by high-energy ball-milling from a powder mixture of zinc oxide (ZnO) and hematite (alpha-Fe(2)O(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. Mossbauer 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+))(B)O(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. (C) 2008 Elsevier B.V. All rights reserved.