Search for: All records

Boron arsenide (BAs) is a covalent semiconductor with a theoretical intrinsic thermal conductivity approaching 1300 W/m K. The existence of defects not only limits the thermal conductivity of BAs significantly but also changes its pressure-dependent thermal transport behavior. Using both picosecond transient thermoreflectance and femtosecond time-domain thermoreflectance techniques, we observed a non-monotonic dependence of thermal conductivity on pressure. This trend is not caused by the pressure-modulated phonon–phonon scattering, which was predicted to only change the thermal conductivity by 10%–20%, but a result of several competing effects, including defect–phonon scattering and modification of structural defects under high pressure. Our findings reveal the complexity of the defect-modulated thermal behavior under pressure.

Methane is a primary component of the “ice” layers in icy bodies whose thermal transport properties and velocity‐density profiles are essential to understanding their unique geodynamic and physiochemical phenomena. We present experimental measurements of methane's thermal conductivity and compressional velocity to 25.1 and 45.1 GPa, respectively, at room temperature, and theoretical calculations of its equation of state, velocity, and heat capacity up to 100 GPa and 1200 K. Overall, these properties change smoothly with pressure and are generally unaffected by the imposed atomic structure; though we observe a discrete spike in conductivity near the I‐A phase boundary. We cross‐plot the thermal conductivity and compressional velocity with density for the primary “ice” constituents (methane, water, and ammonia) and find that methane and water are the upper and lower bounds, respectively, of conductivity and velocity in these systems. These physical properties provide critical insights that advance the modeling of thermo‐chemical structures and dynamics within icy bodies.