The presence of fivefold germanium as a possible transitional phase in the iron–lead–germanate glass system

Abstract

Glasses in the system xFe2O3(100 - x) (7GeO23PbO) with 0 B x B 60 mol% have been prepared from melt quenching method. In this article, we investi- gated changes in germanium coordination number in iron- lead-germanate glasses through molar volume analysis, measurements of densities, investigations of FTIR, and UV-VIS spectroscopy. The observations present in these mechanisms show that the lead ions have an affinity pro- nounced toward (GeO5) and (FeO4) structural units with non-bridging oxygens. The excess of oxygen can be sup- ported into the glass network by the formation of (FeO6) structural units and the apparition of the germanate anomaly. At higher content of iron (III) oxide, the anomaly behavior of the germanium is due to the formations of (FeO6) structural units. Our results show that the presence of fivefold germanium as a possible transitional phase from four to sixfold germanium it is necessary for the formation of the (FeO6) structural units and the apparition of the Fe2O3 crystalline phase. Pb ?2 ions with 6s 2 configuration show strong absorption in the ultraviolet due to parity allowed s 2 -sp transition.