Thermal conductivity measurement at high pressure and high temperature corresponding to deep Earth's condition

The thermal transport properties of the Earth constituent are important information to constrain the thermal evolution and the heat balance of the Earth. In particular, the thermal conductivity and/or the thermal diffusivity of the core, the largest heat source of the Earth, and the lower mantle, occupying more than half the volume of the whole Earth, are indispensable.

In recent years, thermal conductivity measurement on the sample inside the diamond anvil cell has been carried out using the thermoreflectance phenomenon, the reflectance of metal changes greatly due to the temperature perturbation of several kelvin (e.g. Hsieh et al., 2009; Yagi et al., 2011). However, the reported temperature condition is far from Earth's interior conditions.

In this study, we combined the pulsed light heating thermoreflectance method with high power CW laser heating. The thermal conductivities of Pt and Fe were measured up to 52 GPa and 2000 K with this developed system. We found that the thermal conductivities of both metals have positive dependence on both pressure and temperature. These trends are consistent with McWilliams et al. (2015) and Ohta et al. (2016). This apparatus will expand the pressure and temperature conditions for measuring thermal conductivity of deep Earth materials.

Hsieh et al., 2009, Pressure tuning of the thermal conductivity of the layered muscovite crystal, Phys Rev B, 80(18).

Yagi et al., 2011, Thermal diffusivity measurement in a diamond anvil cell using a light pulse thermoreflectance technique, Meas Sci Technol, 22, 024011.

McWilliams et al., 2015, A flash heating method for measuring thermal conductivity at high pressure and temperature: Application to Pt, Phys Earth Planet In, 247, 17-26.

Ohta et al., 2016, Experimental determination of the electrical resistivity of iron at Earth's core conditions, Nature, 534(7605), 95.