PROPERTIES OF BAO-R2O3-GA2O3-GEO2 (R=Y, AL, LA, AND GD) GLASSES

Barium gallogermanate glasses were prepared with substitutions of Al2O3, Y2O3, La2O3, and Gd2O3 for Ga2O3. 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 [AlO4-] tetrahedra substituting directly for [GaO4-] tetrahedra. Yttrium and gadolinium act as ''atypical'' modifier ions because of their large field strengths. Finally, the properties of the La2O3-substituted glasses indicate a possible dual structural role for La3+ ions in these glasses.