Configurational Entropy-Driven Tuning of the Electronic Band Structure of a Semiconducting High Entropy Oxide

High-entropy oxides (HEOs) have recently garnered interest due to their novel thermal and electrical properties, which often differ from those of their parent phases. Previous work on the HEO (Mn,Fe,Co,Ni,Cu,Zn)WO₄ (A⁶WO₄) has shown that increased configurational entropy can lead to a reduction in the band gap and ultra-low thermal conductivity [1-5]. These results also indicate that composition at the high entropy site can significantly affect electronic properties. In this talk, we report the electrical resistivity, thermal conductivity, and Seebeck coefficient as a function of temperature and applied magnetic field for ((Mn, Fe, Co, Ni, Cu, Zn)_1-x (Ru, Rh, Pd) _x )WO₄ (A⁹WO­₄) with x=0.33, 0.5, 0.7. From these results, we find evidence that the electronic properties of A⁹WO­₄ are sensitive even to small changes to the composition of the A site suggesting that precise engineering of the composition could be used to tune electronic properties. We also compare our results to A⁶WO₄ to assess the effect that introducing 4d transition metals has on the thermal and electronic properties of our system. From these comparisons, we find a further reduction in thermal conductivity in A⁹WO­₄ as well as indications that careful doping can open up hole pockets at the Fermi surface.