Refractivity data for aluminosilicate glasses (densities and refractive indices) have been used to examine the relationship between oxygen polarisability, alpha(O2-), and optical basicity, and also to calculate the basicity moderating parameter of the Al3+ ion, gamma(Al). The results indicate that gamma(Al) lies between 1.65 and 1.75, agreeing well with the previously assigned value of 1.65 which is normally employed when dealing with chemical properties such as redox equilibria. This value operates for Al3+ in four-fold coordination. However, refractivity data for crystalline Al2O3, indicate larger values owing to different coordination behaviour (also previously observed for boron and germanium), and for six-fold coordination gamma(Al)=2.5. Trends in gamma(Al) which probably show the presence of six-fold coordinated Al3+ were observed for lithium and magnesium aluminosilicate systems. The results of this study complement density trends in aluminosilicate glasses previously obtained by Doweidar and can be combined with them to predict changes in refractive index effected by changes in glass composition.
|Number of pages||4|
|Journal||Physics and Chemistry of Glasses|
|Publication status||Published - 2003|
- ELECTRONIC POLARIZABILITY
- REDOX EQUILIBRIA
- OXIDE GLASSES