ISSN:
1432-2021
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Abstract The isobaric (P=10 kb) temperature dependence of the electrical conductivities of forsterite, fayalite and forsterite-fayalite mixed crystals was measured with special regard to the thermodynamics of point defects in these minerals. Measurements, taken at increasing and decreasing temperature, were performed on synthetic powders of the following compositions: Fo 100/Fa 0, Fo 90/Fa 10, Fo 80/Fa 20, Fo 60/Fa 40, and Fo 0/Fa100. Control of oxygen partial pressure was achieved with solid state buffers (Fa/Q/M, Fa/Q/I, and Fe/FeO). Activities of the binary components were controlled by equilibrating the sample with its neighbouring phases. All values for σ, obtained with controlled pO2 and fixed activities of the binary components, agree well upon either heating or cooling. From the gradient of lg σ vs. 1/T plots, the following activation energies were estimated: 2,461 eV (970°–1075°C) and 0.984 eV (522°–970°C) for Fo 100/Fa 0 equilibrated with MgO; 0.777 eV and 0.683 eV for Fo 90/Fa 10 and Fo 80/Fa 20 equilibrated with enstatite and pO2 controlled by Fe/FeO buffer; 0.622 eV, 0.528 eV, and 0.479 eV for Fo 90/Fa 10, Fo 80/Fa 20, and Fo 60/Fa 40 equilibrated with enstatite and pO2 controlled by Fa/Q/M buffer; and 0.524 eV and 0.383 eV for Fo 0/Fa 100 equilibrated with Q/I and Q/M respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00311048
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