Potassiumzinc borophosphate glasses were prepared and studied in two compositional series xK2O(50x)ZnO10B2O340P2O5 and
xK2O(50x)ZnO20B2O330P2O5 with x = 0, 10, 20, 30, 40 and 50 mol% K2O. The replacement of zinc by potassium decreases the
density and increases the molar volume of these glasses, whereas glass transition temperature and chemical durability decrease with
increasing potassium content. Structural changes were studied by 11B and 31P MAS NMR and Raman spectroscopy. The observed
changes in the spectra and the properties of the studied glasses can be ascribed to several reasons and namely to the differences in the
space occupied by cations Zn2+ and 2K+, the differences in the electronegativity of zinc and potassium and a large difference in the field
strength of Zn2+ and K+ cations and thus higher ionicity of KO bonds in comparison with ZnO bonds.
Mixed sodiumlead borophosphate glasses were prepared in two compositional series xNa2O(50 - x)PbO10B2O340P2O5 and xNa2O(50 - x)PbO20B2O330P2O5 with x = 0, 10, 20, 30, 40 and 50 mol% Na2O. Their density decreases and molar volume increases slightly with increasing Na2O content. Chemical durability decreases steeply for glasses containing 4050 mol% Na2O, whereas glass transition temperatures reveals a minimum at the glasses with 3040 mol% Na2O. The 31P MAS NMR and Raman spectra of the first series show that with increasing Na2O content the ratio of structural units Q2/Q1 slowly increases and the Q2 phosphate units and BO4 units prevail in the structure of these glasses. In the second series of glasses Q1 diphosphate units together with BO4 and small number of BO3 units form structural network of glasses. The replacement of PbO by Na2O results in higher ionicity of bonding interactions between compensating cations and the anionic network. The lower cation field strength of Na+ ions results in the observed downfield shift of ? (31P) values in Na-rich glasses and narrower vibrational bands in their Raman spectra.
Glasses of the compositional series of 50PbOyB2O3(50-y)P2O5xTiO2 (with x=016) have been prepared and characterized by the determination of density, molar volume, glass transition temperature, dilatation softening temperature, thermal and chemical durability. Structural changes were evaluated from the studies by 31P and 11B MAS NMR, Raman and infrared spectroscopy. Molar volume of the glasses decreases and the glass transition temperature increases with increasing additions of TiO2. 31P MAS NMR spectra revealed that titanate units enter phosphate chains decreasing the number of Q2 units and increasing the number of Q1 units. This result is confirmed by the observed changes in the Raman and infrared spectra of the TiO2-doped glasses.