Enhanced thermoelectric performance of β-Zn4Sb3 based nanocomposites through combined effects of density of states resonance and carrier energy filtering.

Tianhua Zou,Jian Zhang,Hongxing Xin,Anke Weidenkaff,Xiaoguang Li,Yongsheng Zhang,Zhi Zeng,Di Li,Xiaoying Qin,Wenjie Xie

doi:10.1038/srep17803

Abstract

It is a major challenge to elevate the thermoelectric figure of merit ZT of materials through enhancing their power factor (PF) and reducing the thermal conductivity at the same time. Experience has shown that engineering of the electronic density of states (eDOS) and the energy filtering mechanism (EFM) are two different effective approaches to improve the PF. However, the successful combination of these two methods is elusive. Here we show that the PF of β-Zn4Sb3 can greatly benefit from both effects. Simultaneous resonant distortion in eDOS via Pb-doping and energy filtering via introduction of interface potentials result in a ~40% increase of PF and an approximately twofold reduction of the lattice thermal conductivity due to interface scattering. Accordingly, the ZT of β-Pb0.02Zn3.98Sb3 with 3 vol.% of Cu3SbSe4 nanoinclusions reaches a value of 1.4 at 648 K. The combination of eDOS engineering and EFM would potentially facilitate the development of high-performance thermoelectric materials.

Highlights

It is a major challenge to elevate the thermoelectric figure of merit ZT of materials through enhancing their power factor (PF) and reducing the thermal conductivity at the same time
Eq(2) implies that at a given carrier concentration, Scan be enhanced by either increasing N(E), i.e. the electronic density of states (eDOS) at the Fermi level, or the scattering parameter λ, which corresponds to the energy filtering mechanism (EFM)[14]
Zou et al experimentally proved that the introduction of Cu3SbSe4 nanoinclusions increases the thermopower S of β -Zn4Sb3 by EFM22

Summary

Results and Discussion

Because of the enhanced thermopower and decreased resistivity, all β -(Zn1-xPbx)4Sb3 (x = 0.01, 0.02, and 0.03) and f(Cu3SbSe4)/β -Pb0.02Zn3.98Sb3 (f = 2, 3 and 4 vol.%) samples have a higher power factor PF (= S2/ρ) than β -Zn4Sb3 in the whole temperature range (Fig. 1(c)). Linear fitting in the low temperature regime yields the ratio γdop/γun-dop = N(Ef)dop/N(Ef)0un-dop ~3.5 (see Fig. 4) revealing that Pb-doping significantly increases the eDOS at Fermi level This is the largest ZT value ever reported for a β -Zn4Sb3-based systems at 648 K34,40–42

Conclusions

Author Contributions

Additional Information