Glass formation and structure in the system MoO 3–Bi 2O 3–Fe 2O 3

Abstract

The glass formation region in the MoO 3–Bi 2O 3–Fe 2O 3 system was investigated by the roller-quenching method. Glasses melted at temperatures <1400°C were obtained in the MoO 3-rich compositions. Analysis of the glasses was made by X-ray diffraction, differential thermal analysis (DTA), infra-red spectroscopy (IR), and Mössbauer spectroscopy. According to the DTA data, the glass transformation temperature, T g, for the different compositions varies between 360°C and 440°C and the crystallization temperature, T x, is in the range 390–470°C. Structural model for the glasses are suggested on the basis of IR and Mössbauer spectral data. In the region of MoO 3 rich compositions, the network forming units MoO 6 are connected by Mo–O–Mo bridging bonds. The presence of Me 2O 3 (Me=Bi, Fe) leads to transformation of MoO 6 to MoO 4. Thus, in a wide region of compositions the glass network has a scheelite-like structure containing isolated MoO 4 structural units which are surrounded by MeO 6 groups.