Enhanced Average Thermoelectric Figure of Merit of p-Type Zintl Phase Mg2ZnSb2 via Zn Vacancy Tuning and Hole Doping

Yi Niu; Chengcheng Yang; Ting Zhou; Yan Pan; Jie Song; Jing Jiang; Chao Wang

doi:10.1021/acsami.0c09391

Enhanced Average Thermoelectric Figure of Merit of p-Type Zintl Phase Mg₂ZnSb₂ via Zn Vacancy Tuning and Hole Doping

ACS Appl Mater Interfaces. 2020 Aug 19;12(33):37330-37337. doi: 10.1021/acsami.0c09391. Epub 2020 Aug 10.

Authors

Yi Niu¹, Chengcheng Yang¹, Ting Zhou¹, Yan Pan¹, Jie Song¹, Jing Jiang¹, Chao Wang¹

Affiliation

¹ Clean Energy Materials and Engineering Center, State Key Laboratory of Electronic Thin Film and Integrated Device, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.

PMID: 32814413
DOI: 10.1021/acsami.0c09391

Abstract

Isoelectronic Zn substitution at the Mg site has been proved to be effective in regulating the carrier concentration of p-type Mg₃Sb₂ Zintl phase. However, the reported thermoelectric performance is still unsatisfactory compared with that of n-type Mg₃Sb₂ due to the poor electrical transport properties. Here, we report an enhanced average ZT through improving low-temperature ZTs by introducing Zn vacancy followed suppressing the bipolar effect by doping. First, the Zn vacancy simultaneously increases the power factor and decreases the thermal conductivity, leading to a peak ZT value of ∼0.52 at 773 K in Mg₂Zn_0.98Sb₂. Additionally, doping Li or Ag at the Mg site is identified as a high-efficiency strategy for further increasing the carrier concentration and hence suppressing the bipolar effect. Finally, a peak ZT of ∼0.73 at 773 K and an average ZT of ∼0.46 between 300 and 773 K were obtained in Mg_1.98Li_0.02Zn_0.98Sb₂.

Keywords: Mg2ZnSb2; average ZT; bipolar effect; carrier concentration; p-type; zintl phase.