Structure and properties of MoO3-containing zinc borophosphate glasses

ZnO–B2O3–P2O5 glasses doped with MoO3 were investigated in the series (100−x)[0.5ZnO–0.1B2O3–0.4P2O5]–xMoO3, where bulk glasses were obtained by slow cooling in air within the compositional region of 0 ⩽ x ⩽ 60 mol% MoO3. The incorporation of MoO3 into the parent zinc borophosphate glass results in a weakening of bond strength in the structural network, which induces a decrease in chemical durability and glass transition temperature. Raman spectra reflect the incorporation of molybdate groups into the glass network of the studied glasses by the presence of the polarized vibrational band at ≈976 cm−1 ascribed to the MOx symmetric stretching vibrations and the depolarized band at ≈878 cm−1 ascribed to the Mo–O–Mo stretching vibration. The incorporation of molybdate units into the glass network results in the depolymerization of phosphate chains and the formation of P–O–Mo bonds, as reflected in Raman and 31P NMR spectra. According to the 11B MAS NMR spectra, tetrahedral B(OP)4−x(OMo)x units are formed in the glasses, whereas only a small amount of BO4 units is converted to BO3 units in the MoO3-rich glasses.