The Structure And Properties Of Zinc Aluminophosphate Glasses

The glass forming region of the ZnO-Al ₂ O ₃ -P ₂ O ₅ (ZAP) system was determined and the structures and properties of the glasses were characterized. For glasses with a constant O/P ratio, i.e., with similar average phosphate anion distributions, and with increasing alumina content, there is an increase in molar volume and glass transition temperature and a decrease in density and refractive index. The structures of the ZAP glasses were characterized by Raman spectroscopy, ³¹ P and ²⁷ Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and high pressure liquid chromatography (HPLC). Systematically shorter phosphate anions constitute the structures of glasses with greater O/P ratios. The average aluminum coordination number (CN _Al ) changes systematically with composition, from ~ 4.0 to ~ 5.6, depending on the number of terminal oxygens available to coordinate each Al-cation. Glass properties are sensitive to both the types and concentrations of the P-anions as well as the CN _Al . © 2013 Elsevier B.V.