| 1 | High-Performance Mg_(3)Sb_(2-x)Bi_(x) Thermoelectrics:Progress and Perspective显示文摘Since the first successful implementation of n-type doping,low-cost Mg_(3)Sb_(2-x)Bi_(x) alloys have been rapidly developed as excellent thermoelectric materials in recent years.An average figure of merit zT above unity over the temperature range 300-700 K makes this new system become a promising alternative to the commercially used n-type Bi_(2)Te_(3-x)Se_(x) alloys for either refrigeration or low-grade heat power generation near room temperature.In this review,with the structure-property-application relationship as the mainline,we first discuss how the crystallographic,electronic,and phononic structures lay the foundation of the high thermoelectric performance.Then,optimization strategies,including the physical aspects of band engineering with Sb/Bi alloying and carrier scattering mechanism with grain boundary modification and the chemical aspects of Mg defects and aliovalent doping,are extensively reviewed.Mainstream directions targeting the improvement of zT near room temperature are outlined.Finally,device applications and related engineering issues are discussed.We hope this review could help to promote the understanding and future developments of low-cost Mg_(3)Sb_(2-x)Bi_(x) alloys for practical thermoelectric applications. | Airan Li Chenguang Fu Xinbing Zhao Tiejun Zhu | 2020 | Research2020，，1： | 4 |
| 2 | Violation of the T^(−1) Relationship in the Lattice Thermal Conductivity of Mg_(3)Sb_(2) with Locally Asymmetric Vibrations显示文摘Most crystalline materials follow the guidelines of T^(-1) temperature-dependent lattice thermal conductivity(κ_(L))at elevated temperatures.Here,we observe a weak temperature dependence ofκL in Mg_(3)Sb_(2),T^(-0:48) from theory and T-0:57 from measurements,based on a comprehensive study combining ab initio molecular dynamics calculations and experimental measurements on single crystal Mg_(3)Sb_(2).These results can be understood in terms of the so-called“phonon renormalization”effects due to the strong temperature dependence of the interatomic force constants(IFCs).The increasing temperature leads to the frequency upshifting for those low-frequency phonons dominating heat transport,and more importantly,the phononphonon interactions are weakened.In-depth analysis reveals that the phenomenon is closely related to the temperature-induced asymmetric movements of Mg atoms within MgSb_(4) tetrahedron.With increasing temperature,these Mg atoms tend to locate at the areas with relatively low force in the force profile,leading to reduced effective 3^(rd)-order IFCs.The locally asymmetrical atomic movements at elevated temperatures can be further treated as an indicator of temperature-induced variations of IFCs and thus relatively strong phonon renormalization.The present work sheds light on the fundamental origins of anomalous temperature dependence of κ_(L) in thermoelectrics. | Yifan Zhu Yi Xia Yancheng Wang Ye Sheng Jiong Yang Chenguang Fu Airan Li Tiejun Zhu Jun Luo Christopher Wolverton GJeffrey Snyder Jianjun Liu Wenqing Zhang | 2020 | Research2020，，1： | 0 |
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