Towards higher zT in early transition metal oxides: optimizing the charge carrier concentration of the WO3-x compounds

Abstract

Thermoelectric devices are believed to play an important role in the energy research for the next decades. Thanks to their low costs coupled with high stability and sustainability, metal oxides are very promising materials even if their efficiencies still need improvements to ensure a wide applicability. Slightly reduced early transition metal oxides show intrinsic defects in the crystal structure which guarantee very low values of the thermal conductivity. The challenge to fulfil the “phonon-glass electron-crystal” concept is to decouple the optimization of the electronic properties from the thermal transport properties. In this contribution we report the optimization of the charge carrier concentration in the Magnéli phase WO2.90 through the manipulation of the oxygen content. Keeping the thermal conductivity constant and increasing the electronic transport we manage to rise the figure of merit of a 30% compared to the non-optimized sample.