TRENDS IN LOCAL OPTICAL BASICITY IN SODIUM-BORATE GLASSES AND RELATION TO IONIC MOBILITY

Far infrared spectra of alkali borate glasses indicate two distinct site distributions for the alkali ions. A newly established relationship between optical basicity and infrared frequency allows the optical basicities of these sites to be evaluated, and the trends, with increasing alkali oxide, are presented for the Na2O-B2O3 glass system. These upper and lower optical basicity trends are close to experimental values obtained from probe ion spectroscopy in the ultraviolet region using Tl+. Furthermore, in a 35 mol% Na2O glass, for which the optical basicity values are 0.45 and 0.65, the spectra of Tl+ ions electrolysed into the glass indicate that the mobile Na+ ions are chiefly those in the higher basicity site.