Infrared studies of Na2O-B2O3-SiO2 and Al2O3-Na2O-B2O3-SiO2 glasses

Infrared spectra of Na2O-B2O3-SiO2 and Al2O3-Na2O-B2O3-SiO2 glasses (with intermediate SiO2 contents) have been analyzed to calculate the fraction N-4 of four coordinated borons. A reasonable agreement between the N-4 values calculated from IR spectra and those determined from NMR spectroscopy (or using literature models) could be attained under certain condition. It has been proposed that the absorption bands in the region 1000-1120 cm(-1) arise from contributions Of SiO2 and B2O3 vibrations. The contribution of an oxide is proportional to its concentration. Heat treatment of Na2O-B2O3-SiO2 glasses does not change the value of N-4 and this indicates that the structure of alkali borate phase is the same in the glass obtained -from melt and in the heat-treated one. (C) 2002 Elsevier Science B.V. All rights reserved.