Measurements of lattice thermal conductivity of MgO to core‐mantle boundary pressures

The pressure response of lattice thermal conduction in MgO periclase has been a matter of interest for many decades to estimate the thermal conductivity profile of the lower mantle. Using the pulsed light heating thermoreflectance technique, we measured the lattice thermal diffusivity of MgO at pressures up to 137 GPa at 300 K to determine its lattice thermal conductivity under deep lower mantle conditions. Considering the temperature effect estimated by previous high‐temperature measurements, we calculated the lattice part of the thermal conductivity of MgO to be 17.9 ± 1.1 W/m/K at 135 GPa and 3600 K. Additionally, we observed that the lattice conductivity of MgO has little dependence on its grain size under core‐mantle boundary conditions.