Calorimetric study of the coesite-stishovite transformation and calculation of the phase boundary

J. Liu, L. Topor, J. Zhang, A. Navrotsky, R. C. Liebermann

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52 Scopus citations

Abstract

High temperature drop-solution calorimetry in molten 2 PbO · B2O3 at 1044 K for coesite and stishovite polymorphs of silica was carried out to determine the enthalpy of the coesite-stishovite transition. These experiments were performed on high-purity, single-phase samples of coesite and stishovite. Our new value for the enthalpy of the coesite-stishovite transition (ΔH2980) is 29.85 ± 0.78 kJ/mol, which is about 35% lower than previously reported by Akaogi and Navrotsky (1984) and Holm et al. (1967), but which compares well with new measurements by Akaogi et al. (1994b). Using these new data, we have calculated the equilibrium phase boundary between coesite and stishovite and obtained a slope, dP/dT=0.0031 (2) GPa/ K. This calculated slope is in good agreement with that determined [0.0026 (2) GPa/K] from the in-situ X-ray diffraction study of Zhang et al. (1996).

Original languageEnglish (US)
Pages (from-to)11-16
Number of pages6
JournalPhysics and Chemistry of Minerals
Volume23
Issue number1
DOIs
StatePublished - Feb 1996
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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