Structural characterization of glassy phases in the system Na2O-Ga2O3-P2O5by MAS-NMR, EXAFS and vibrational spectroscopy. I. Cations coordination

The cationic coordinations of phosphate based gallium sodium glasses in the system Na2O-Ga2O3-P(2)0(5) have been studied by several techniques (Ga-71 and Na-23 MAS-NMR, EXAFS and vibrational spectroscopies) in order to study the relationship between the structure and the chemical composition. We fou nd that three different environments are available for the gallium ions whi le it is very difficult to get accurate information on the sodium coordinat ions. Our data show that in orthophosphate glasses, gallium is mainly tetra hedral but when the mean phosphate chain length increases, its coordination becomes more and more octahedral. In these glassy structure, it becomes th en possible to dissolve large amounts of typically octahedral cations like Fe3 + or Cr3 +. (C) 2000 Elsevier Science B.V. All rights reserved.