Leveraging crystal symmetry for thermoelectric performance optimization in cubic GeSe  

作　　者：Yu-Geng Li Yong-Qiang Liu Mo-Ran Wang Wen-Qing Yao Xiao-Huan Luo Tu Lyu Wei-Qin Ao Chao-Hua Zhang Fu-Sheng Liu Li-Peng Hu 

机构地区：[1]College of Materials Science and Engineering,Institute of Deep Earth Sciences and Green Energy,Shenzhen Key Laboratory of Special Functional Materials,Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization,Guangdong Research Center for Interfacial Engineering of Functional Materials,Shenzhen University,Shenzhen 518060,China

出　　处：《Rare Metals》2024年第10期5332-5345,共14页稀有金属（英文版）

基　　金：financially supported by the National Key R&D Program of China(No.2021YFB1507403);the National Natural Science Foundation of China(No.52071218);Shenzhen Science and Technology Innovation Commission(No.JCYJ20230808105700001);Shenzhen University 2035 Program for Excellent Research(No.00000218)。

摘　　要：In thermoelectrics,the manipulation of crystal symmetry is instrumental in optimizing the electrical and thermal transport parameters.Within this context,the present study explored the largely overlooked high-symmetry cubic GeSe,which presented larger band degeneracy than its widely studied medium-symmetry rhombohedral counterpart.We have successfully stabilized cubic Ge Se a ambient conditions through co-alloying with AgSnTe_(2)and Bi.The incorporation of AgSnTe_(2)initiates the transition of GeSe from a low-symmetry orthorhombic to a mediumsymmetry rhombohedral phase,culminating in a highsymmetry cubic structure,underpinned by variation in chemical bonding mechanisms.Notwithstanding this,the persistence of Ag_(2)Te precipitates impedes the total elimination of the residual orthorhombic phase due to the disparate chemical bonding mechanism between Ag_(2)Te and GeSe.Introducing Bi into the rhombohedral-dominated(GeSe)_(0.7)(AgSnTe_(2))_(0.3)matrix leads to the dissolution of Ag_(2)Te precipitates,elimination of the residual orthorhombic phase,and the subsequent stabilization of the exclusive cubic phase.Compared to its orthorhombic counterpart,the cubic GeSe exhibits diminished bandgap and Ge vacancy formation energy,amplified band degeneracy,reduced sound velocity,intensified lattice anharmonicity and multiple phonon scattering centres engendering elevated carrier concentration and density-ofstates effective mass,alongside restrained lattice therma conductivity.Consequently,a peak zT of 0.46 at 573 K is attained for cubic(Ge_(0.7)Bi_(0.3)Se)_(0.7)(AgSnTe_(2))_(0.3),signifying a ninefold increase relative to the initial orthorhombic Ge Se.These results illuminate the critical role of crystal symmetry manipulation in advancing the thermoelectric performance.

关 键 词：THERMOELECTRIC GeSe Crystal symmetry High-entropy alloying Band degeneracy 

分 类 号：TB34[一般工业技术—材料科学与工程]