Electronic polarisabilities of rare earth metal ions are obtained from refractivity data (densities and refractive indices) for their crystalline trifluorides in order to make viable an analysis of refractivity data for silicate, aluminosilicate and phosphate glasses containing rare earth oxides. These data provide for each glass a value of the electronic polarisability of the oxide (-II) atoms from which is calculated the optical basicity. In turn, this allows assignment of the basicity moderating parameter gamma, to the rare earth ion present in the glass. For La3+ and Nd3+, gamma is 0.85 (expressed to the nearest 0.05), corresponding to optical basicities, A, for the oxides La2O3 and Nd2O3 of 1.18. These oxides are therefore more basic than calcium oxide. The gamma and A values allow the basicity of a glass composed of these oxides to be expressed numerically on the optical basicity scale. Data that are available for phosphate glasses include all the rare earth ions (except Pm3+) and indicate a very irregular trend in gamma, but with an overall increase from La3+ to Lu3+ (which has gamma=1.03, approximately). This trend corresponds to an overall decrease in oxide basicity from La2O3 to Lu2O3, which is in accordance with the well known lanthanide contraction effect. There is evidence for the phosphate glasses that the rare earth oxides can behave as network formers in spite of their high basicity.
|Number of pages||5|
|Journal||Physics and Chemistry of Glasses|
|Publication status||Published - 2005|
- ELECTRONIC POLARIZABILITY
- UV TRANSPARENCY
- OXIDE GLASSES