Role of aluminium in the silicate network: In situ, high-temperature study of glasses and melts on the join SiO 2-NaAlO 2
Abstract
The structure of glasses and melts in the NaAlSiO 2-SiO 2 system was determined in situ as a function of temperature by Raman spectroscopy, in the temperature range of 300 K-1800 K. The high-frequency envelope of the Raman spectra of Al-free SiO 2 glass is deconvoluted in three different bands (1050, 1150, and 1200 cm -1) with the 1150 and 1200 cm -1 bands attributed to Si-O 0 stretch vibrations in Q 4 species in the fully polymerized network. There is a decrease in their frequencies with increasing Al/(Al + Si) of the glasses and melts in the Al/(A1 + Si) range investigated (0-0.5). The spectra are consistent with Al 3+Si 4+ substitution in two coexisting, three-dimensionally interconnected structural units. These units have different average intertetrahedral angles. Aluminum partitions preferentially into the unit with the smaller angle at low Al/(Al + Si) (less than ~0.3), and into the unit with the larger angle at higher concentrations. There is no evidence for major structural changes (i.e., redistribution of Al) in the glasses and melts as a function of increasing temperature.
- Publication:
-
Geochimica et Cosmochimica Acta
- Pub Date:
- May 1996
- DOI:
- 10.1016/0016-7037(96)00049-X
- Bibcode:
- 1996GeCoA..60.1727N