STRUCTURE OF VITREOUS AND MOLTEN B2O3 MEASURED BY PULSED NEUTRON TOTAL SCATTERING

The temperature dependence of structure of vitreous and molten B2O3 has been measured from 121 K, through the glass transition temperature Tg of 540 K, to 1073 K by means of pulsed neutron total scattering technique. The characteristic changes of both the structure factors S(Q) and the radial distribution functions RDF have been observed. The analyses of the S(Q)s in the high Q region and of the clear peaks observed in the RDF curves suggest that the structure of BO3 units does not change significantly with increasing temperature, while the connectivity of these units changes with increasing temperature especially above Tg. Further, the observed temperature dependence of the position of the first peak of S(Q) differs significantly below and above Tg, and is closely related to that of the observed density. From these observations, the following are suggested: the basic structural units are packed isotropically below Tg but are packed anisotropically like a chain above Tg. © 1990.