Ultrahigh Power Factor in Thermoelectric System Nb0.95M0.05FeSb (M = Hf, Zr, and Ti).

Wuyang Ren,Chao Wang,Jun Mao,Qing Zhu,Zhifeng Ren,Zihang Liu,Zhiming Wang,Hangtian Zhu,Udara Saparamadu,Kornelius Nielsch,Ran He

doi:10.1002/advs.201800278

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.

Highlights

Thermoelectric materials are capable to power factor (PF), respectively
A higher ZT will result in a higher η, improvement of ZT has been the goal for the thermoelectric a temperature difference of ≈560 K, showing the realistic prospect of the ultrahigh PF for power generation
We demonstrate a material system Nb0.95M0.05FeSb (M = Hf, Zr, Ti) with significantly enhanced PF to ≈100 μW cm−1 K−2 at room temperature

Summary

Results and Discussion

The σ of Hf- and Zr-doped samples hot pressed at 1173 K exhibit T−0.67 and T−0.58 dependence at lower temperature range, respectively, which implies the mixed scattering mechanism being dominant.[60,61]. Due to both Hf and Zr are quite efficient dopants to supply carriers, the similar nH was achieved (see Table S1 in the Supporting Information). A large ωmax of ≈21.6 W cm−2 was obtained at the TC of ≈313 K and TH of ≈873 K, demonstrating the excellent performance of Nb0.95Hf0.05FeSb in power generation

Conclusion

Experimental Section

Conflict of Interest