A HIGH-TEMPERATURE ELECTRICAL-CONDUCTION MECHANISM IN THE LOWER MANTLE PHASE (MG,FE),O1-X

Measurements of electrical conductivity at high pressure and temperatu re were taken on the lower mantle phase magnesiowustite with varying F e3+ content. Although previous measurements at atmospheric pressure su ggest Fe2+-Fe3+ hopping (small polaron) as the dominant conductivity m echanism, the present experiments show a change in charge transport me chanism with temperature. The lower temperature measurements are consi stent 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 co mpositional dependencies, this transition has important implications f or extrapolation to mantle conditions.