Microstrain Release Decouples Electronic and Thermal Conductivity in Powder Aerosol Deposited Films

Decoupling electronic and thermal conductivity in nanostructured materials has been a major challenge in the field of electronics and thermoelectrics. Using powder aerosol deposition (PAD) in combination with photothermal post-treatment, we report a nanostructured material where the electric conductivity drastically increases without affecting the thermal conductivity. Working with delafossite, CuFe0.98Sn0.02O2, we demonstrate that PAD results in films with a significant microstrain between the nanosized crystallites. Photothermal treatment releases the atomic lattice strain but retains the nanocrystalline structure. We interpret that the increase in conductivity results from a higher charge carrier mobility due to a reduction in lattice deformation. In contrast, the nanocrystalline microstructure leads to a low thermal film conductivity, which is unaffected by the posttreatment. This unique observation paves the way to unravel a mechanism to access materials with an improved thermoelectric figure of merit.