Ultrahigh Power Factor in Thermoelectric System Nb_0.95M_0.05FeSb (M = Hf, Zr, and Ti)

Abstract

Conversion efficiency and output power are crucial parameters for thermoelectric power generation that highly rely on figure of merit ZT and power factor (PF), respectively. Therefore, the synergistic optimization of electrical and thermal properties is imperative instead of optimizing just ZT by thermal conductivity reduction or just PF by electron transport enhancement. Here, it is demonstrated that Nb0.95Hf0.05FeSb has not only ultrahigh PF over ≈100 µW cm−1 K−2 at room temperature but also the highest ZT in a material system Nb0.95M0.05FeSb (M = Hf, Zr, Ti). It is found that Hf dopant is capable to simultaneously supply carriers for mobility optimization and introduce atomic disorder for reducing lattice thermal conductivity. As a result, Nb0.95Hf0.05FeSb distinguishes itself from other outstanding NbFeSb‐based materials in both the PF and ZT. Additionally, a large output power density of ≈21.6 W cm−2 is achieved based on a single‐leg device under a temperature difference of ≈560 K, showing the realistic prospect of the ultrahigh PF for power generation.

Thermoelectric property enhancement by merging bands in NbFeSb-based half-Heusler mixtures

“…It is interesting to note that, at a high temperature ($1000 K), the zT of n-type (0.62) and p-type (0.72) of Nb 4 Mn 2 Co 2 Sb 4 are comparable, which suggests that it is possible to simultaneously achieve high thermoelectric performance for both ntype and p-type legs within the same material framework. Even though the lattice thermal conductivities of the mixtures are already lower than that of NbFeSb, their thermoelectric properties can be further improved using defect engineering, such as doping Ti and Hf as in NbFeSb 50,58,63 to optimize the carrier concentration and further reduce the thermal conductivity. With a similar methodology, the theoretically predicted Nb 4 Mn 2 Co 2 Sb 4 would reach a higher zT value.…”

High‐Pressure‐Sintering‐Induced Microstructural Engineering for an Ultimate Phonon Scattering of Thermoelectric Half‐Heusler Compounds

“…Other than (Bi,Sb) 2 Te 3 , microstructural engineering applies to other materials for phonon scattering. [ 7–10 ] Among the widely studied thermoelectric materials, half‐Heusler compounds are particularly promising due to their unique advantages such as a high power factor, [ 11–14 ] or mechanical and chemical robustness, [ 15,16 ] employment of abundant and nontoxic elements, etc. On the other hand, these compounds usually possess a large κ L that hinders their zT improvement.…”

High Thermoelectric Performance of Cu-Doped PbSe-PbS System Enabled by High-Throughput Experimental Screening

“…Optimizing the performance of a thermoelectric material is relatively difficult due to its adversely interdependent transport parameters [12][13][14][15]. Specifically, the performance of a thermoelectric material depends on the dimensionless figure of merit, zT, which is defined as zT = σS 2 T/ðκ e + κ L Þ, where σ, S, κ e , κ L , and T are the electrical conductivity, Seebeck coefficient, electrical thermal conductivity, lattice thermal conductivity, and absolute temperature, respectively [16]. Thus, in order to improve thermoelectric performance, these transport parameters should be synergistically optimized.…”