M. Malki

Carbonatite Melts and Electrical Conductivity in the Asthenosphere

Electrically conductive regions in Earths mantle have been interpreted to reflect the presence of either silicate melt or water dissolved in olivine. On the basis of laboratory measurements, we show that molten carbonates have electrical conductivities that are three orders of magnitude higher than those of molten silicate and five orders of magnitude higher than those of hydrated olivine. High conductivities in the asthenosphere probably indicate the presence of small amounts of carbonate melt in peridotite and can therefore be interpreted in terms of carbon concentration in the upper mantle. We show that the conductivity of the oceanic asthenosphere can be explained by 0.1 volume percent of carbonatite melts on average, which agrees with the carbon dioxide content of mid-ocean ridge basalts.

Methodological re-evaluation of the electrical conductivity of silicate melts

Abstract Electrical impedance measurements in the laboratory on silicate melts are used to interpret magnetotelluric anomalies. On the basis of 2- and 4-electrode measurements, we show that the influence of the electrodes of the 2-electrode system on the measured resistivity can be of significant importance for low-resistivity melts and increases with temperature. At 1400 °C, the resistivity of very conductive melts measured with two electrodes can reach six times the resistivity value measured with four electrodes. A short-circuit experiment is needed to correct the 2-electrode data. Electrodes contribution is also estimated for samples from other studies, for which the resistance of the electrical cell can be as high as the resistance of the sample. A correction of the resistivity data from the literature is proposed and values of the corresponding Arrhenian parameters are recommended.

Fast-ion conduction and flexibility of glassy networks.

We observe two thresholds in the variations of electrical conductivity of dry (AgI)_{x}(AgPO3)_{1-x} solid electrolyte glasses, when the AgI additive concentration x increases to 9.5% and to 37.8%. Raman scattering complemented by calorimetric measurements confirms that these thresholds are signatures of the rigidity phase transitions at x=9.5% from a stressed rigid to an isostatically (stress-free) rigid phase, and at x=37.8% from isostatically rigid to a flexible phase. In the flexible phase, the electrical conductivity seems to increase as a power of x. This is in good agreement with the theoretical prediction based on 3D percolation.

Fast-ion conduction and flexibility and rigidity of solid electrolyte glasses

Electrical conductivity of dry, slow cooled (AgPO

Elastic flexibility, fast-ion conduction, boson and floppy modes in AgPO3?AgI glasses

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Electrical conductivity of the CaO-SiO2 system in the solid and the molten states

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Electrical conductivity measurements of oxides from molten state to glassy state

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Designing heavy metal oxide glasses with threshold properties from network rigidity

(AgI)

Rigidity transitions in glasses driven by changes in network dimensionality and structural groupings

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Electrical conductivity of synthetic mullite single crystals

glasses is examined as a function of temperature, frequency and glass composition. From these data compositional trends in activation energy for conductivity E