Large thermoelectric power factor in one-dimensional telluride Nb4SiTe4 and substituted compounds

We found that whisker crystals of Mo-doped Nb4SiTe4 show high thermoelectric performances at low temperatures, indicated by the largest power factor of ∼70 μW cm−1 K–2 at 230–300 K, much larger than those of Bi2Te3-based practical materials. This power factor is smaller than the maximum value in the 5d analogue of Ta4SiTe4 but is comparable to that with a similar doping level. First principles calculation results suggest that the difference in thermoelectric performances between Nb and Ta compounds is caused by the much smaller bandgap in Nb4SiTe4 than that in Ta4SiTe4 due to the weaker spin-orbit coupling in the former. We also demonstrated that the solid solution of Nb4SiTe4 and Ta4SiTe4 shows a large power factor, indicating that their combination is promising as a practical thermoelectric material, as in the case of Bi2Te3 and Sb2Te3. These results advance our understanding of the mechanism of high thermoelectric performances in this one-dimensional telluride system, indicating the high potential of this system as a practical thermoelectric material for low temperature applications.