Glass formation and structure of glasses in the Y2O3-Fe2O3-B2O3 system

Abstract

An extensive region of glass formation and liquid immiscibility have been found in the Y2O3—Fe2O3—B2O3 system. The glass transition and crystallization temperatures were determined for selected single phase glasses in this system. The glass transition temperature and the stability of the glass were found to decrease with increasing concentration of Fe2O3 . Mössbauer spectroscopy, infrared spectroscopy and transmission electron microscopy were used to obtain an insight into the structure of these glasses. Infrared and Mössbauer spectra indicate that, similar to the Y2O3—Al2O3—B2O3 system, glasses in the above system contain (FeB2O6)∞ chains composed of FeO4-tetrahedral and BO3-triangular structural units. Hyperfine splitting phenomena were observed in the Mössbauer spectra of glasses containing high Fe2O3 concentrations. The appearance of such hyperfine lines, and the decrease in the isomer shift with increasing Fe2O3 content, suggest formation of iron-rich microclusters, which is supported by the presence of microstructure at a very fine scale. Glasses with increasing Y2O3 concentration showed a decrease in the isomer shift and quadrupole spliting. Glases containing TiO2 yielded A-Fe2O3 when crystallized.