Structural role and coordination environment of Fe in Fe2O3–PbO–SiO2–Na2O composite glasses (original) (raw)

The structural role, coordination geometry and valence of Fe in a series of Fe 2 O 3-PbO-SiO 2-Na 2 O glasses are studied by means of Fe-K-NEXAFS and EXAFS spectroscopies. Parameters for the study are the concentration of the Fe and Pb-oxides, the SiO 2 /Na 2 O ratio and the cast temperature. The EXAFS and NEXAFS results reveal that the role of Fe 3+ depends on the concentration of Fe 2 O 3. More specifically, in most of the studied quaternary systems, the Fe 3+ ion is a glass former, i.e. the Fe atoms belong to FeO 4 tetrahedra that participate in the formation of the glassy network. The role of Fe as an intermediate oxide is identified only in one sample with 20 wt% Fe 2 O 3 , where 80at.80 at.% of the Fe atoms are tetrahedrally coordinated with O atoms, while the remaining 80at.20 at.% of the Fe atoms occupy octahedral sites. It is also revealed that the tetrahedral coordination of Fe in the vitreous matrix is destroyed when a number of parameters is altered, such as the T cast , the (Fe + Si)/O and the SiO 2 /Na 2 O ratio.