Alkali distribution in borosilicate glasses

The alkali distribution in borosilicate glass has been discussed on the basis of the different quantities obtained by various experimental methods. The NBO fraction was chosen as a common quantity for evaluating the alkali distribution models. The NBO fractions in sodium borosilicate glasses were estimated from ¹¹B and ²⁹Si NMR as well as XPS. However, the best model was not found among the existing models. The amounts of sodium oxide consumed for the NBO formation in borate and silicate networks and for the formation of BO₄ units were separately estimated from the ¹¹B and ²⁹Si NMR data. A new trend was found in the alkali distribution suggesting the possibility for a new universal distribution model.