Electric conductivity of glasses in the system Na2O/CaO/SiO2/Fe2O3

The addition of polyvalent transition metal ions to the usually insulating traditional soda-lime-silica glasses can lead to semiconducting properties. We report on synthesis of glasses and glass-ceramics in a soda-lime-silicate based system containing Fe2O3 in the concentration range from 5 to 30 mol%. Two sub-systems were considered, in one of them the ratio [Na2O]/[Fe2O3] was varied while in the other one, the ratio [SiO2]/[Fe2O3] was changed. The phase composition of the synthesized products was characterized by X-ray diffraction and energy dispersive X-ray analysis, while the electrical properties were studied by impedance spectroscopy. Partially crystallized nonreduced samples are semiconducting even at room temperature while the glassy samples (both reduced and non-reduced) exhibit semiconducting properties at temperatures equal or larger than 100 degrees C. An attempt is done to predict the physical approximation explaining the conduction process in the glasses. (c) 2007 Elsevier B.V. All rights reserved.