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Quartz and Cristobalite: high‐temperature cell parameters and volumes of fusion
Author(s) -
Bourova Ekatarina,
Richet Pascal
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl01581
Subject(s) - cristobalite , quartz , fusion , volume (thermodynamics) , enthalpy of fusion , materials science , analytical chemistry (journal) , melting point , mineralogy , thermal expansion , molar volume , tridymite , melting temperature , temperature coefficient , thermodynamics , chemistry , composite material , physics , chromatography , philosophy , linguistics
The cell parameters of quartz and cristobalite have been measured up to their melting points from X‐ray diffraction experiments with synchrotron radiation. After a smooth increase up to 1300 K, the volume of β‐cristobalite decreases continuously up to the melting temperature of 2000 K where it is back to the 750 K value of 27.4 cm³/mol. A slightly negative thermal expansion coefficient is also observed for quartz above 1400 K, resulting in a volume of 23.45 cm³/mol at 1673 K. From these results and the molar volume of SiO 2 liquid, the volumes of fusion of β‐cristobalite and quartz are −0.1 and 3.85 cm³/mol, respectively. With these values and the known entropies of fusion, only a slight adjustment to 1673 K of the melting temperature of quartz has been found necessary to ensure consistency with available phase equilibria data.