(GeTe)1- x(AgSnSe2)x: Strong Atomic Disorder-Induced High Thermoelectric Performance near the Ioffe-Regel Limit

Gege Liang; Tu Lyu; Lipeng Hu; Wanbo Qu; Shizhen Zhi; Jibiao Li; Yang Zhang; Jian He; Junqin Li; Fusheng Liu; Chaohua Zhang; Weiqin Ao; Heping Xie; Haijun Wu

doi:10.1021/acsami.1c14801

(GeTe)_{1- x}(AgSnSe₂)_x: Strong Atomic Disorder-Induced High Thermoelectric Performance near the Ioffe-Regel Limit

ACS Appl Mater Interfaces. 2021 Oct 6;13(39):47081-47089. doi: 10.1021/acsami.1c14801. Epub 2021 Sep 27.

Authors

Gege Liang¹, Tu Lyu^{1

2}, Lipeng Hu¹, Wanbo Qu³, Shizhen Zhi¹, Jibiao Li⁴, Yang Zhang⁵, Jian He⁶, Junqin Li¹, Fusheng Liu¹, Chaohua Zhang¹, Weiqin Ao¹, Heping Xie¹, Haijun Wu³

Affiliations

¹ College of Materials Science and Engineering, Shenzhen Key Laboratory of Special Functional Materials, Guangdong Research Center for Interfacial Engineering of Functional Materials, Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization, Institute of Deep Earth Sciences and Green Energy, Shenzhen University, Shenzhen 518060, China.
² College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
³ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
⁴ Center for Materials and Energy (CME) and Chongqing Key Laboratory of Extraordinary Bond Engineering and Advanced Materials Technology (EBEAM), Yangtze Normal University, Chongqing 408100, China.
⁵ Instrumental Analysis Center of Xi'an Jiaotong University, Xi'an Jiaotong University, Xi'an 710049, China.
⁶ Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634-0978, United States.

PMID: 34565145
DOI: 10.1021/acsami.1c14801

Abstract

In thermoelectrics, the material's performance stems from a delicate tradeoff between atomic order and disorder. Generally, dopants and thus atomic disorder are indispensable for optimizing the carrier concentration and scatter short-wavelength heat-carrying phonons. However, the strong disorder has been perceived as detrimental to the semiconductor's electrical conductivity owing to the deteriorated carrier mobility. Here, we report the sustainable role of strong atomic disorder in suppressing the detrimental phase transition and enhancing the thermoelectric performance in GeTe. We found that AgSnSe₂ and Sb co-alloying eliminates the unfavorable phase transition due to the high configurational entropy and achieve the cubic Ge_1-x-ySb_yTe_1-x(AgSnSe₂)_x solid solutions with cationic and anionic site disorder. Though AgSnSe₂ substitution drives the carrier mean free path toward the Ioffe-Regel limit and minimizes the carrier mobility, the increased carrier concentration could render a decent electrical conductivity, affording enough phase room for further performance optimization. Given the lowermost carrier mean free path, further Sb alloying on Ge sites was implemented to progressively optimize the carrier concentration and enhance the density-of-state effective mass, thereby substantially enhancing the Seebeck coefficient. In addition, the high density of nanoscale strain clusters induced by strong atomic disorders significantly restrains the lattice thermal conductivity. As a result, a state-of-the-art zT ≈ 1.54 at 773 K was attained in cubic Ge_0.58Sb_0.22Te_0.8(AgSnSe₂)_0.2. These results demonstrate that the strong atomic disorder at the high entropy scale is a previously underheeded but promising approach in thermoelectric material research, especially for the numerous low carrier mobility materials.

Keywords: GeTe; Ioffe−Regel limit; atomic disorder; high entropy alloys; thermoelectric.