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

In this study, we systematically investigate the thermoelectric properties of (Nb_xW_1-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 W^{5 +} 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 μV/K and achieves a remarkable zT value of approximately 0.318 at 800℃. 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 (Nb_xW_1-x)₁₈O₄₉ Pentacolumn structures for high-temperature thermoelectric applications.