Properties of BaO-R sub(2)O sub(3)-Ga sub(2)O sub(3)-GeO sub(2) (R identical with Y,Al,La and Gd) glasses

Barium gallogermanate glasses were prepared with substitutions of Al sub(2)O sub(3), Y sub(2)O sub(3), La sub(2)O sub(3), and Gd sub(2)O sub(3) for Ga sub(2)O sub(3). The effects of these substitutions on the glass transformation temperature, viscosity, thermal expansion, and molar volume have been determined. The changes in properties associated with each substitutional ion are consistent with structural roles reported for these ions in other glasses. Aluminum acts as an intermediate with [AlO super(-) sub(4)] tetrahedra substituting directly for [GaO super(-) sub(4)] tetrahedra. Yttrium and gadolinium act as `atypical' modifier ions because of their large field strengths. Finally, the properties of the La sub(2)O sub(3)-substituted glasses indicate a possible dual structural role for La super(3+) ions in these glasses.