Effect of annealing on the structural role of Fe in composite Fe- and Zn-rich materials: A XAFS study

摘要

We report on composition- and annealing-related modifications in the local bonding environment of Fe in a series of Fe- and Zn-rich composite quaternary materials whose composition models stabilized electric-arc furnace dust wastes. Application of X-ray absorption fine structure spectroscopies revealed that when [Fe_2O_3 ] < 20 wt%, Fe~(3+) is a glass former, i.e. Fe belongs to tetrahedral sites into the vitreous matrix, independently of the annealing process and chemical composition. On the contrary, when [Fe_2O_3 ] > 20 wt% the samples become vitroceramic. It is disclosed that a fraction of Fe~(3+) occupies octahedral sites in Zn_zFe_(3-x)O_4 crystalline inclusions which are embedded into the glass matrix where the rest of Fe~(3+) is bonded in tetra-hedra. Furthermore, annealing of the samples with [Fe_2O_3] ≥ 20 wt% at 900℃ induces devitrification, the samples become crystalline and Fe~(3+) belongs to Zn_nFe_(3-n)O_4 where it forms both FeO_4 tetrahedra and FeO_6 octahedra.