ISSN:
1432-2021
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Abstract Measurements of conductivity and thermopower as a function of oxygen fugacity (ƒO 2) are used to derive a model for conduction in olivine. Thermopower at 1000–1200 °C is between 50 and 400 μV/K and has a positive ƒO 2 dependence, and electrical conductivity exhibits approximately a 1/11 power dependence on ƒO 2. However, small polarons, considered to be the conducting defect in olivine at these temperatures, would produce a larger thermopower than observed, with a negative ƒO 2 dependence, as well as 1/6 power dependence of conductivity on ƒO 2. At least one other conducting defect species must be invoked to explain the observed magnitude and ƒO 2 dependence of thermopower. An electron/polaron model cannot be made to fit the conductivity and thermopower data well, but a polaron/magnesium vacancy model fits the data if a constant polaron or magnesium vacancy term is included. Concentrations from our fits are consistent with predictions from theoretical models, and our analysis predicts a transition from polaron dominance in conduction to magnesium vacancy dominance at around 1300 °C, as has been previously inferred from other data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002690050044
