On the local coordination of Fe in Fe2O3-glass and Fe2O3-glass ceramic systems containing Pb, Na and Si

The effect of the composition and casting temperature on the structural role of Fe in a series of binary (Fe2O3–PbO and Fe2O3–Na2O) and ternary (Fe2O3–PbO–SiO2) glass and glass ceramic materials is studied by means of X-ray fluorescence (XRF) mapping, X-ray absorption fine structure (XAFS) and Mössbauer spectroscopies. According to the Mössbauer results the majority of Fe exists in the Fe+3 state. The XRF maps reveal that Fe-rich islands evolve into the vitreous matrix of ternary samples that contain more than 40 wt% Fe2O3. In these samples the XAFS results disclose that 40–43 at.% of the Fe atoms belong to the Fe-rich microcrystalline islands formed by FexOy oxides. Furthermore, the structural role of Fe+3 in the ternary glasses is found to depend on the Fe2O3 content. Finally in the binary Fe2O3–PbO systems the majority of Fe+3 is octahedrally coordinated in the Fe2O3 and/or PbFe12O19 crystalline phases.