A High-Temperature Electrical Conduction Mechanism in the Lower Mantle Phase (Mg,Fe)1−xO

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Science  21 Mar 1997:
Vol. 275, Issue 5307, pp. 1779-1781
DOI: 10.1126/science.275.5307.1779

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Measurements of electrical conductivity at high pressure and temperature were taken on the lower mantle phase magnesiowüstite with varying Fe3+ content. Although previous measurements at atmospheric pressure suggest Fe2+-Fe3+ hopping (small polaron) as the dominant conductivity mechanism, the present experiments show a change in charge transport mechanism with temperature. The lower temperature measurements are consistent with small polaron conduction, but at higher temperatures, which are more applicable to the lower mantle, a large polaron mechanism is suggested. Because these mechanisms have different temperature and compositional dependencies, this transition has important implications for extrapolation to mantle conditions.

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