Determination of the crystallization ratio in a series of Fe-containing vitroceramic products by means of XAFS spectroscopies

We apply X-ray fluorescence (XRF) mapping and Fe-K X-ray absorption fine structure (XAFS) spectroscopies in order to determine the elemental distribution, the local coordination of Fe and the crystallization ratio of vitroceramic compounds that consist of Fe2O3, PbO, SiO2 and Na2O. The XRF maps reveal that Fe-rich inclusions are embedded into the vitreous matrix of the studied samples. The XAFS characterization results demonstrate that all quaternary samples are vitroceramic independently of the chemical composition and the Tcast. The ΕXAFS analysis reveals that only in the sample with 45 wt% Fe2O3 and Tcast = 1400 °C the microcrystalline inclusions consist of magnetite units. In all other vitroceramic samples the crystalline regions comprise both hematite and magnetite crystallites. The crystallization ratio is equal among all the vitroceramic samples, independent of the composition and Tcast. On the other hand, the increase in the concentration of hematite causes an elongation of the Fe–O bondlength in the FeO6 polyhedra and thus improves the symmetry of the FeO6 octahedra in the crystalline regions.