Abstract
Ternary thallium and sodium bismuth germanate glasses were prepared and their densities refractive indices, and infra-red spectra obtained. The effect of univalent cations on the stability of the arrangement of decoupled GeO4 tetrahedra in amorphous Bi4Ge3O12 was compared with the effect of divalent cations. The molar volumes of glasses with the nominal mol% composition 20 M2O(MO).20 Bi2O3.60 GeO2 are directly related to the size and charge type of Mz+. However, the molar volumes of such glasses are inversely related to the ionic potential (z/r) of Mz+. The infra-red spectra of these ternary glasses exhibitvGe−O shifts that reflect the presence of both isolated and small clusters of GeO4 tetrahedra compared to amorphous Bi4Ge3O12. This slight increase in the degree of polymerization appears to be directly related to the ionic potential of Mz+.
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