Structural and Mossbauer characterization of the ball milled Fex(Cr2O3)1-x system

The Fe-x(Cr2O3)(1-x) system, with 0.10 <= X <= 0.80, was mechanically processed for 24 h in a high-energy ball-mill. in order to examine the possible formation of iron-chromium oxides and alloys, the milled samples were, later, thermally annealed in inert (argon) and reducing (hydrogen) atmospheres. The as-milled and annealed products were characterized by X-ray diffraction, Mossbauer spectroscopy, transmission electron microscopy and magnetization. The as-milled samples showed the formation of an Fe1+YCr2-YO4-delta nanostructured and disordered spinel phase, the alpha(1)-Fe(Cr) and alpha(2)-Cr(Fe) solid solutions and the presence of non-exhausted precursors. For the samples annealed in inert atmosphere, the chromite (FeCr2O4) formation and the recrystallization of the precursors were verified. The hydrogen treated samples revealed the reduction of the spinel phase, with the phase separation of the chromia phase and retention of the Fe-Cr solid solutions. All the samples, either as-milled or annealed, presented the magnetization versus applied field curves typical for superparamagnetic systems. (C) 2009 Elsevier Masson SAS. All rights reserved.