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GEOREF RECORD

Crystallization of cristobalite and tridymite in the presence of vanadium

Petra Bruhns and Reinhard X. Fischer
Crystallization of cristobalite and tridymite in the presence of vanadium
European Journal of Mineralogy (June 2000) 12 (3): 615-624

Abstract

The formation of cristobalite and tridynute compounds is described in the system SiO (sub 2) -V (sub 2) O (sub 5) -M (sub 2) CO (sub 3) [M = Na. K). Syntheses were performed with various vanadium concentrations at annealing temperatures between room temperature and 1000 degrees C. Crystallization of cristobalite occurs at much lower temperatures (about 800 degrees C) in the presence of vanadium than observed in the pure silica system, which remains amorphous in this temperature range. With increasing amounts of vanadium, the crystallization of NaVO (sub 3) or K (sub 3) V (sub 5) O (sub 14) is observed along with the formation of cristobalite and tridymite. XRD. IR. and NMR indicate that cristobalite is formed by catalytic processes in the presence of vanadium without measurable V-substitution in its structure. Variations in the thermal behavior of cristo- balite are attributed to different states of crystallinity.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 12
Serial Issue: 3
Title: Crystallization of cristobalite and tridymite in the presence of vanadium
Affiliation: Universitaet Bremen, Fachbereich Geowissenschaften, Bremen, Federal Republic of Germany
Pages: 615-624
Published: 200006
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 26
Accession Number: 2000-049404
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200016
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