Electrical conductivity of calcite between 300 and 1200/sup 0/C
Recent high-pressure work on the phase relations of CaCO/sub 3/ revealed two high-temperature transitions of calcite located at one atmosphere at 800 and 990/sup 0/C resp. Extending Bridgman's terminology (1939) these high-temperature phases are referred to as calcite IV and calcite V. Structural considerations suggest anion disorder as the transition mechanism. The experiments were conducted with a conventional two Pt-electrode arrangement under some 50 atm CO/sub 2/ pressure, employing dc (10 V) as well as ac (10 to 60 V/50 Hz). Cleavage fragments of calcite single crystals served as samples. According to the relation delta = delta/sub 0/ exp -E/kT the conductivities and activation energies for different temperature intervals were calculated. These data, additionally supported by measurements of the emf-polarity, suggest that the intrinsic conduction of calcite above 800/sup 0/K may rely mainly on anionic disorder. The almost pressure independent conductivity interval between 1075 to 1175/sup 0/K insinuates a critical disorder state of the calcite IV phase. This tentative interpretation seems to be supported by the behavior of the unit cell parameters and the intensity of reflections specific for CO/sub 3/-groups obtained from high-temperature x-ray powder photographs.
- Research Organization:
- Ruhr-Univ., Bochum, Ger.
- OSTI ID:
- 5342320
- Journal Information:
- EOS, Trans., Am. Geophys. Union; (United States), Vol. 57:12; Conference: AGU fall annual meeting, San Francisco, CA, USA, 6 Dec 1976
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCITE
ELECTRIC CONDUCTIVITY
CARBON DIOXIDE
CRYSTAL-PHASE TRANSFORMATIONS
HIGH TEMPERATURE
MEDIUM PRESSURE
VERY HIGH TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CARBONATES
CHALCOGENIDES
ELECTRICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
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