GLASS-FORMATION AND STRUCTURE IN THE SYSTEM MOO3-BI2O3-FE2O3

The glass formation region in the MoO3-Bi2O3-Fe2O3 system was investig ated by the roller-quenching method. Glasses melted at temperatures <1 400 degrees C were obtained in the MoO3-rich compositions. Analysis of the glasses was made by X-ray diffraction, differential thermal analy sis (DTA), infra-red spectroscopy (IR), and Mossbauer spectroscopy. Ac cording to the DTA data, the glass transformation temperature, T-g, fo r the different compositions varies between 360 degrees C and 440 degr ees C and the crystallization temperature, T-x, is in the range 39-470 degrees C. Structural model for the glasses are suggested on the basi s of IR and Mossbauer spectral data. In the region of MoO3 rich compos itions, the network forming units MoO6 are connected by Mo-O-Mo bridgi ng bonds. The presence of Me2O3 (Me=Bi, Fe) leads to transformation of MoO6 to MoO4. Thus, in a wide region of compositions the glass networ k has a scheelite-like structure containing isolated MoO4 structural u nits which are surrounded by MeO6 groups. (C) 1998 Elsevier Science B. V. All rights reserved.