X-RAY PHOTOELECTRON-SPECTROSCOPY OF AL-SUBSTITUTED AND B-SUBSTITUTED SODIUM TRISILICATE GLASSES

X-ray photoelectron spectroscopy (XPS) has revealed physical and chemical structure differences between aluminum and boron substituted sodium silicate glasses, Na2O . xR2O3 . (3 - 2X)SiO2, prepared by a melt quench method, where R = Al or B, and x = 0, 0.2, 0.4, 0.6, 0.8, 1. The structure of sodium aluminosilicate (SAS) glasses deduced from the analysis of XPS data is found to agree with the four-coordinated aluminum structure model with Na balancing the local charge. The structure of sodium borosilicate (SBS) glasses is mostly consistent with Bray's model with the need to consider a 'contending factor' for Na. Sodium is not fully ionized as often assumed. Its ionicity increases in both SAS and SBS glasses with increasing Al/B substitution. Net charge on atoms according to Pauling's model has been calculated as a guidance in analyzing the XPS spectra.