[SIT22-P19] High P-T electrical resistivity measurements on iron in an internally-heated diamond anvil cell
Keywords:planetary core, electrical conductivity, iron, high pressure experiment, internal heating method
A laser-heated diamond anvil cell (LHDAC) technique is commonly used for measurement of physical properties of deep Earth materials at high pressure (P) and temperature (T) conditions. However, the laser heating produces large temperature gradient in the heated area and is difficult to maintain stable heating. Direct measurements of the electrical and thermal conductivities of iron (Fe) in a LHDAC have been reported (Konôpková et al., 2016; Ohta et al., 2016). The reported electrical conductivity at 135 GPa and 3700 K corresponding to the Earth’s core-mantle boundary (CMB) condition (Ohta et al., 2016) is 3~4 times higher than the one estimated from thermal conductivity measurements (Konôpková et al., 2016). It is possible that a large temperature gradient in their Fe samples due to laser heating caused the discrepancy between the two studies.
Here we employed an internally-heated diamond anvil cell (IHDAC) technique to measure electrical resistivity (inverse of conductivity) of Fe at high P-T conditions. The experiments were carried out at 50 and 70 GPa and up to ~2500 K. We found this heating method could achieve much lower temperature gradient in the sample than the laser heating. Our results show that the electrical resistivity of Fe at high P-T conditions is slightly higher than the value reported by Ohta et al. (2016). Our estimates of Fe conductivity at high P-T would give the new constraints on the transport properties of the Earth's core.
Ohta, K., Y. Kuwayama, K. Hirose, K. Shimizu, and Y. Ohishi (2016), Experimental determination of the electrical resistivity of iron at Earth’s core conditions, Nature, 534, 95–98, doi:10.1038/nature17957.
Konôpková, Z., R. McWilliams, N. Gómez-Pérez, and A. Goncharov (2016), Direct measurement of thermal conductivity in solid iron at planetary core conditions, Nature, 534, 99–101, doi:10.1038/nature18009.