Optimizing seebeck coefficient and thermoelectric efficiency via innovative Nb doping techniques in W18O49

In this study, we systematically investigate the thermoelectric properties of (NbxW1-x)18O49 compounds (0 <= x <= 0.20). Unlike conventional doping approaches that aim to introduce additional charge carriers to enhance electrical conductivity, our non-conventional method focuses on tuning the electronic structure of the W18O49 matrix by substituting W5 + with Nb5+ cations. This substitution reduces the maximum number of donating electrons from 108 to approximately 104, approaching the 98 electrons accepted by the anions. This electronic tuning results in a significant increase in the Seebeck coefficient to-133.717 mu V/K and achieves a remarkable zT value of approximately 0.318 at 800 degrees C. Additionally, Nb doping induces notable structural distortions, leading to modifications in morphology and a reduction in lattice thermal conductivity. Despite a decrease in electrical conductivity with higher Nb content, the overall thermoelectric performance is enhanced, highlighting the potential of (NbxW1-x)18O49 Pentacolumn structures for high-temperature thermoelectric applications.