Morphological and Structural Investigations on Iron Borosilicate Glasses

Borosilicate glasses and glass ceramics in the system 30Na₂O-2Al₂O₃-25SiO₂-xFe₂O₃(43-x)B₂O₃ (x = 0 - 20 mol%) have been prepared and studied by distinguished techniques. X-ray diffraction (XRD), transmission electron microscope (TEM), electron diffraction pattern (EDP) and SEM experiments are applied to explore the induced structural changes. Nanometer-sized species of polycrystalline structure are formed particularly in low Fe₂O₃ containing glasses. The size of the crystallites is found to depend on Fe₂O₃ concentrations. It is ranged from 10 to 33 nanometers. Structurally, these materials are suggested to contain different components, crystalline component and an interfacial component which situated between the crystallized domains. Presence of these components affects the atomic arrangement without short- or long-range order. An intermediate range ordered structure is dominant in glass ceramics of Fe₂O₃ < 8 mol%. Less ordered structure is dominated in glasses of higher Fe₂O₃ concentration, since more disordered structure of lower size is present. These structural changes are found to be connected with the role of Fe₂O₃ and Na₂O in glasses. Na₂O is the strong glass modifier in the studied composition region, while Fe₂O₃ is consumed also as a modifier in composition of < 8 mol%. Glass forming character of Fe₂O₃ is mainly dominant in the composition region of higher iron oxide concentration (8 - 20 mol%).