Reversibility of the synthesis-decomposition reaction in the ball-milled Cu-Fe-O system

In this work, we present results from a ball-milling experiment carried out simultaneously on (a) spinel and (b) its precursor mixture , to investigate their evolution under identical conditions. Partial reversibility of the reaction was observed, resulting in nearly equal phase composition for both systems after 420 h of milling. X-ray data showed that the final admixture was composed mainly of nanosized and spinel phases. Almost coincident average grain sizes were found in both milled samples, although different size distributions were inferred from their magnetic behaviour. Superparamagnetic (SPM) relaxation effects were observed in the resulting particles at room temperature. Mössbauer and magnetization data taken below the SPM blocking temperature indicate partial formation of the (0 < x < 1) spinel solid solution, with cubic structure and high local disorder.