Modulation of transport properties of RuO₂ with 3d transition metals

Using density functional theory, we have demonstrated that alloying of RuO₂ (P4₂/mnm) with 3d transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) gives rise to a substantial increase in the Seebeck coefficient probably due to quantum confinement. As Fe yields the largest enhancement, it was selected for experimental verification. We synthesized combinatorial Ru–Fe–O thin films and subsequently measured their transport properties at elevated temperatures. The Fe-alloyed samples increase the Seebeck coefficient threefold with respect to the unalloyed RuO₂ specimen thereby verifying the theoretical prediction. The here obtained power factor of 274 μW K⁻² m⁻¹ is not only the largest reported value for RuO₂ based compounds but it also occurs at ∼600 °C thus increasing the Carnot efficiency significantly. (paper)