title: Phase Segregation and Superior Thermoelectric Properties of Mg2Si(1-x)Sb(x) (0 ≤ x ≤ 0.025) Prepared by Ultrafast Self-Propagating High-Temperature Synthesis.
abstract: A series of Sb-doped Mg2Si(1-x)Sb(x) compounds with the Sb content x within 0 ≤ x ≤ 0.025 were prepared by self-propagating high-temperature synthesis (SHS) combined with plasma activated sintering (PAS) method in less than 20 min. Thermodynamic parameters of the SHS process, such as adiabatic temperature, ignition temperature, combustion temperature, and propagation speed of the combustion wave, were determined for the first time. Nanoprecipitates were observed for the samples doped with Sb. Thermoelectric properties were characterized in the temperature range of 300-875 K. With the increasing content of Sb, the electrical conductivity σ rises markedly while the Seebeck coefficient α decreases, which is attributed to the increase in carrier concentration. The carrier mobility μ(H) decreases slightly with the increasing carrier concentration but remains larger than the Sb-doped samples prepared by other methods, which is ascribed to the self-purification process associated with the SHS synthesis. In spite of the increasing electrical conductivity with the increasing Sb content x, the overall thermal conductivity κ decreases on account of a significantly falled lattice thermal conductivity κ(L) due to the strong point defect scattering on Sb impurities and possibly enhanced interface scattering on nanoprecipitates. As a result, the sample with x = 0.02 achieves the thermoelectric figure of merit ZT ∼ 0.65 at 873 K, one of the highest values for the Sb-doped binary Mg2Si compounds investigated so far. A subsequent annealing treatment on the sample with x = 0.02 at 773 K for 7 days has resulted in no noticeble changes in the thermoelectric transport properties, indicating an excellent thermal stability of the compounds prepared by the SHS method. Therefore, SHS method can serve as an effective alternative fabrication route to synthesize Mg-Si based themoelectrics and some other functional materials due to the resulting high performance, perfect thermal stability, and feasible production in large scale for commercial application.
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.|Key Laboratory of Interface Science and Engineering in Advanced Materials, Ministry of Education, Taiyuan University of Technology , Taiyuan 030024, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Xianli
authors.initials: X
authors.lastname: Su
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Yonggao
authors.initials: Y
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Hongyao
authors.initials: H
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Yonghui
authors.initials: Y
authors.lastname: You
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology , Wuhan 430070, China.
authors.forename: Xinfeng
authors.initials: X
authors.lastname: Tang
authors.affiliation: Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Ctirad
authors.initials: C
authors.lastname: Uher
keywords: Mg2Si1−xSbx; phase segregation; self-propagating high-temperature synthesis; thermal stability; thermoelectric properties