Energetics of the Charge-Coupled Substitution Si4+ Na++ T3+ in the-Glasses NaTO2–SiO2 (T = Al, Fe, Ga, B)

Yoreo, James J. de; Navrotsky, Alexandra und Dingwell, Donald B. (1990): Energetics of the Charge-Coupled Substitution Si4+ Na++ T3+ in the-Glasses NaTO2–SiO2 (T = Al, Fe, Ga, B). In: Journal of the American Ceramic Society, Bd. 73, Nr. 7: S. 2068-2072

Abstract

Heats of solution in molten 2PbO·B2O3 at 973 K are reported for glasses xNaT3+O2–(1 –x)SiO2 for T = Fe, Ga. These measurements, combined with previous data for T = Al, B, give a relative measure of the enthalpy of the charge-coupled substitution Si4+→ Na++ T3+. The heats of solution become more endothermic with increasing x for x→ 0.5 and exhibit a maximum near x= 0.5. This indicates an exothermic enthalpy for the substitution and an overall stabilization of the glasses. The degree to which the glasses are stabilized decreases in the order Al > Ga > Fe > B. On the basis of molecular orbital calculations, X-ray scattering, and Raman spectroscopy, it is argued that this trend is primarily due to a decrease in the range of energetically favorable T–O–T bond angles as Al, Ga, Fe, and B are substituted for Si.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften > Mineralogie, Petrologie und Geochemie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• Sprache: Englisch