GLASS-FORMATION AND LOCAL-STRUCTURE IN THE TERNARY-SYSTEM P-SE-AL - SOLID-STATE NMR-STUDIES

Glasses in the system phosphorus-selenium-aluminum have been prepared by ice-water quenching of sealed ampoules. X-ray powder diffraction an d differential scanning calorimetry (DSC) of samples indicate a limite d region of glass formation a in the selenium-rich region of the compo sition diagram. Structural studies using Al-27 and P-31 solid state NM R reveal that the local environments of both aluminum and phosphorus a re dominated by selenium, however, multiple environments are observed for both glass constituents. The presence of aluminum enhances the ten dency of phosphorus to become four-coordinate, suggesting that both gl ass formers interact in the network to some extent. On the other hand, dipolar solid state NMR studies indicate that the P ... Al interactio ns are generally smaller than expected on the basis of statistically l inked PSex and AlSex polyhedra. Together with DSC results, these data favor a structure that is at least partially segregated and/or phase s eparated. (C) 1998 Elsevier Science B.V.