Unusual coordination numbers in silicate and aluminate glasses
- Arizona State Univ., Tempe, AZ (United States)
- Stanford Univ., Palo Alto, CA (United States)
Silicon and aluminum are the principal network-forming cations in silicate and aluminosilicate glasses. In most models of glass structure, these are presumed to be in tetrahedral coordination, except for highly aluminous compositions, where VI-coordinated Al is expected. Al{sup VI} and Si{sup VI} species have also been suggested to be formed at high pressure. Recent work has yielded some interesting results regarding the Al and Si coordination chemistry in glasses. In amorphous Al{sub 2}O{sub 3} films prepared by electrochemical deposition, not only Al{sup IV} and Al{sup VI}, but also Al{sup V} species have been recognized. These species have also been observed in glasses and amorphous phases prepared along the SiO{sub 2}-Al{sub 2}O{sub 3} join. The concentration of the five coordinated Al species is highly dependent on composition and glass preparation conditions. Al{sup V} and Al{sup VI} species have also recently been described along the SiO{sub 2}-MgAl{sub 2}O{sub 4} join, where it was previously supposed that all Al was tetrahedral. The behavior of silicon is even more {open_quotes}surprising{close_quotes}. In experiments on alkali silicate glasses quenched from high pressures, the authors found evidence for Si in VI-fold coordination, as expected from high pressure silicate crystal structures, and also for Si{sup V}, a new species in silicate chemistry. The relative abundances of these species are a function of quench pressure and silica content. The Si{sup V} species has also been observed in trace amounts in room pressure glasses, and the authors have investigated its concentration as a function of alkali cation.
- OSTI ID:
- 141408
- Report Number(s):
- CONF-930304-; TRN: 93:003688-1085
- Resource Relation:
- Conference: 205. American Chemical Society national meeting, Denver, CO (United States), 28 Mar - 2 Apr 1993; Other Information: PBD: 1993; Related Information: Is Part Of 205th ACS national meeting; PB: 1951 p.
- Country of Publication:
- United States
- Language:
- English
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