Glass formation and structure of glasses in the ZnO―Bi 2O 3―WO 3―MoO 3 system

Abstract

The glass formation region in the ternary ZnO―Bi 2O 3―WO 3 system is determined by melt quenching technique (cooling rates 10 1–10 2 K/s). New original glasses are obtained in a narrow concentration range with high WO 3 content (60–75 mol%). Homogeneous glasses of the composition (100 − x)[0.2ZnO·0.3Bi 2O 3·0.5WO 3]xMoO 3, were obtained between 20 and 60 mol% MoO 3. 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 MoO 3 content. The glass transition temperature, T g, varies between 340–480 °C, while the crystallization temperature, T x, varies between 388–531 °C. The tungstate glasses possess higher crystallization temperature (T x 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 WO 3 into a layered one, consisting mainly of WO 6 units. We supposed that the network of quaternary glasses is built up by MoO 4, MoO 6 and WO 6. At low concentration ZnO and Bi 2O 3 facilitate the disorder in the supercooled melts, while at high concentration stimulate crystallization processes. These oxides belong to the intermediate ones.