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

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