A SPECTROSCOPIC INVESTIGATION OF ANHYDROUS KALSI3O8 AND NAALSI3O8 GLASSES QUENCHED FROM HIGH-PRESSURE

Al-27 MAS NMR, Raman, and IR spectra were collected for high-pressure NaAlSi3O8 and KAlSi3O8 glass samples, produced by isobarically quenching melts from pressures up to 10 GPa, to investigate the effect of pressure on the structure of fully polymerized aluminosilicate melts. The spectra are consistent with a decrease in the average TOT angle within the tetrahedral framework with increasing pressure. No obvious new peaks were observed in the spectra which could be assigned to high-coordinate aluminum in the high-pressure glasses. Some broadening at the base of the Al-27 MAS NMR peak could be associated with the presence of some high-coordinate aluminum species, but this could also result from increased distortion of the intertetrahedral linkages.