Doping dependence of thermoelectric performance in Mo₃Sb ₇: First-principles calculations

We study the effects of doping Mo₃Sb₇ with transition metals (Ni, Fe, Co, Ru) via first-principles calculations, including electronic structure, lattice dynamics, and Boltzmann transport. We find heavy-mass bands and large, rapidly varying density of states, generally favorable for high thermopower, near the band gap of this material. Transport calculations predict large Seebeck coefficients exceeding 300 μV/K in a wide temperature range above 500 K (a range suitable for waste heat recovery), if the material can be doped into a semiconducting state. These thermopowers are much higher than those that have previously been experimentally observed; we find that performance exceeding current limits may be found at lower carrier concentration than achieved presently. We also discuss the selection of dopant and the potential thermoelectric performance of optimally doped Mo₃Sb₇.