Structure and energetics of vitreous and crystalline tectosilicates

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

The energetics of complex framework silicates is related to their structure and composition in a systematic fashion. This is illustrated by thermochemical data for crystalline silicas including zeolites and the silica polymorphs, and for amorphous silicas, including glasses, CVD and sol-gel materials. Relative to quartz as the stable crystalline polymorph and bulk glass as the most stable amorphous form, enthalpy increases with both increasing density (coesite, stishovite and pressure or radiation densified glasses) and with decreasing density (tridymite, cristobalite, zeolitic silicas, sol-gel and CVD amorphous structures). Preliminary data suggest the most open structures (e.g. faujasite approaching SiO2 in composition) are not as destabilized as their large molar volume would imply, suggesting that large pores, with normal framework density between them, are more stable than a relatively uniform expansion of structure. Coupled substitution: Si4+ = (l/n) Mn+ + T3+ stabilizes tectosilicates. Stabilization increases in the order M = Mg, Ca, Sr, Ba, Li, Na, K, Rb, Cs and in the order T = B, Fe3+, Ga, Al, that is, with increasing basicity of the nonframework cation and with increasing similarity to Si of the cation substituting in the framework. These trends are discussed in terms of structure and bonding.

Original languageEnglish (US)
Title of host publicationTransactions of the American Crystallographic Association
EditorsAdrian C. Wright
PublisherPubl by American Crystallographic Assoc
Pages1-12
Number of pages12
ISBN (Print)0937140368
StatePublished - 1991
Externally publishedYes
EventProceedings of the Symposium on The Structural Chemistry of Silicates - Toledo, OH, USA
Duration: Jul 22 1991Jul 24 1991

Publication series

NameTransactions of the American Crystallographic Association
Volume27
ISSN (Print)0065-8006

Conference

ConferenceProceedings of the Symposium on The Structural Chemistry of Silicates
CityToledo, OH, USA
Period7/22/917/24/91

ASJC Scopus subject areas

  • Engineering(all)

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