Electrical conductivity of iron under shock compression up to 200 GPa

Abstract

The electrical conductivity of shock-compressed iron was measured up to 208 GPa by using an improved sample assembly in which the iron sample is encapsulated in a single-crystal sapphire cell. High-pressure shock compressions were generated by plate impact with a two-stage light-gas gun. The measured conductivity of iron varies from 1.45 × 104 Ω −1 cm−1 at 101 GPa and 2010 K, to 7.65 × 103 Ω−1 cm−1 at 208 GPa and 5220 K. After analysing these data together with those reported previously, we found that the Bloch–Grüneisen expression is valid for ε-iron in the pressure and temperature range up to 208 GPa and 5220 K.

Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T , and heat flux in Earth’s core

“…1) closely agree with the shock compression measurements of Keeler (10) and the lowest pressure point of Bi et al (11), at pressures where Hugoniot temperatures (25) are comparable to those in our simulations. Similarly, values for Fe 3 Si liquid are in agreement with the shock measurements of Matassov (12) for the same composition.…”

“…Lower pressure shock compression measurements are at progressively lower temperatures; the 18 GPa measument of Keeler (10) is at 320 K, and agrees well with room temperature static measurements in hcp Fe (17,18), adding confidence to the shock compression resistivity data, and our results. In light of the large scatter in the Bi et al (11) dataset, and the serious disagreement between the data of Bi et al (11) and Keeler (10) above 120 GPa, we feel that comparison of our results with the measurements of Keeler (10) is more appropriate. Computed low pressure resistivity for pure Fe liquid is somewhat smaller than experimental values (26,27), yet computed ambient pressure thermal conductivity does agree closely with experimental estimates for liquid Fe at temperatures above melting (1,810 K) (28).…”

“…Existing estimates of thermal conductivity (k el ) and electrical resistivity (ρ el ) of Earth's outer core are based on extrapolations (8, 9) of resistivity measurements in shock-compressed Fe and Fe-Si alloys (10)(11)(12) to core temperatures and pressures. These extrapolations assume the direct proportionality of electrical resistivity to temperature, its invariability along and across the Fe liquidus, and adherence to the Wiedemann-Franz law, which relates electrical resisitivity and thermal conductivity for metals through the Lorenz number (13) …”

Electrical resistivity and thermal conductivity of hcp Fe–Ni alloys under high pressure: Implications for thermal convection in the Earth’s core

“…Adding the impurity resistivity of silicon and nickel, Stacey and Anderson (2001) gave 2.12 Â 10 À6 X m and 2.02 Â 10 À6 X m at the CMB and the ICB, respectively. Then, new shock compression experiment was reported up to 200 GPa (Bi et al, 2002). Bi and others suggested the possibility that resistivity was underestimated in earlier shock wave experiments because of the melting of insulating epoxy at high temperature.…”

“…Bi and others suggested the possibility that resistivity was underestimated in earlier shock wave experiments because of the melting of insulating epoxy at high temperature. Considering the new measurement (Bi et al, 2002), both Davies (2007) and Stacey and Loper (2007) revised the estimate by Stacey and Anderson (2001) downwardly. Davies (2007) calculated 1.25-1.9 Â 10 À6 X m for pure iron and 2.15-2.80 Â 10 À6 X m for Fe-Si alloy at the CMB.…”