Mixed alkali effect on density, refractive index and related properties of alkali borate glasses

The density and refractive index of single and mixed alkali borate glass systems have been measured and used to calculate the molar volume molar refractivity and molar refractivity of oxygen ion in order to investigate the configurational changes that might be induced in the glass structure as the constituent alkali ion is gradually replaced by another: A slight deviation from linearity was observed only in the density composition relation for glasses containing 20 mol% (Na2O-K2O). The deviation significantly increases with increasing (Na2O-K2O) content but does not exceed 1% which suggests that the observed deviation does not result from a large scale structural rearrangement of the local network of mixed alkali borate glasses.