Glass formation and structure of glasses in the ZnO―Bi2O3―WO3―MoO3 system

The glass formation region in the ternary ZnO―Bi2O3―WO3 system is determined by melt quenching technique (cooling rates 101–102 K/s). New original glasses are obtained in a narrow concentration range with high WO3 content (60–75 mol%). Homogeneous glasses of the composition (100 − x)[0.2ZnO·0.3Bi2O3·0.5WO3]xMoO3, were obtained between 20 and 60 mol% MoO3. Characterization of the amorphous samples was made by x-ray diffraction (XRD), differential thermal analysis (DTA) and infrared spectroscopy (IR). The thermal stability of glasses decreases with the increasing of MoO3 content. The glass transition temperature, Tg, varies between 340–480 °C, while the crystallization temperature, Tx, varies between 388–531 °C. The tungstate glasses possess higher crystallization temperature (Tx over 500 °C) in comparison with the other vanadate and molybdate non-traditional glasses. The glass network is realized by transformation of three-dimensional structure of WO3 into a layered one, consisting mainly of WO6 units. We supposed that the network of quaternary glasses is built up by MoO4, MoO6 and WO6. At low concentration ZnO and Bi2O3 facilitate the disorder in the supercooled melts, while at high concentration stimulate crystallization processes. These oxides belong to the intermediate ones.