Thermal conductivity of ordered-disordered material: a case study of superionic Ag2Te
Thermal conductivity of ordered-disordered material: a case study of superionic Ag2Te
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DOI：
10.1088/0957-4484/26/2/025702
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发表时间：
2015-01
期刊：
影响因子：
3.5
通讯作者：
T. Ouyang;Xiaoliang Zhang;Ming Hu
中科院分区：
文献类型：
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作者：
T. Ouyang;Xiaoliang Zhang;Ming Hu
热电装置可以从废热中发电，为解决全球不断增长的能源需求中的一个重要利基市场提供了一条有吸引力的途径。在过去的几十年里，对高效热电材料的研究一直受到“声子玻璃电子晶体”（PGEC）概念的指导，即理想的热电材料应具有高载流子迁移率和低热导率。虽然在这方面已经取得了沿着的进步，但热电的效率仍然太低，无法与其他发电方法竞争。有序-无序材料是PGEC概念下高性能热电材料的一种新兴趋势，是当前热电研究界的一个新热点。以超离子相银碲化物（α-Ag 2 Te）为例，采用平衡态分子动力学模拟方法，对该体系的热输运性质及其物理机制进行了全面的研究.结果表明，α-Ag_2Te的热导率很低。通过分析对整体热导率的不同贡献，我们首次从原子模拟中揭示了Te 2 −亚晶格的振动主导了α-Ag 2 Te的热输运，而随机扩散的Ag+离子与Te 2 −亚晶格之间的碰撞对热输运产生了显着的负贡献。研究了各向同性压应变和载流子浓度对α-Ag_2Te热导率的影响。已经发现，通过施加压缩应变或化学计量量调制，可以大大降低热导率。我们的研究揭示了有序-无序材料中热输运的控制机制，并可为工程设计超离子导体的热输运性质以提高其热电性能提供有用的指导。
Thermoelectric devices, which can generate electricity from waste heat, offer an attractive pathway for addressing an important niche in the globally growing landscape of energy demand. In the past few decades, the search for high-efficiency thermoelectrics has been guided by the concept of ‘phonon-glass electron-crystal’ (PGEC), i.e. an ideal thermoelectric material should have high carrier mobility and low thermal conductivity. Although remarkable progress has already been made along this line, the efficiency of thermoelectrics is still too poor to compete with other electricity producing methods. Ordered-disordered material, an emerging trend of high performance thermoelectrics under the concept of PGEC, is a new hot topic in the current thermoelectric research community. Taking superionic phase silver telluride (α-Ag2Te) as an example, we performed a comprehensive study of the thermal transport properties and of its physical mechanism by means of equilibrium molecular dynamic simulations. The results show that the thermal conductivity of α-Ag2Te is intrinsically very low. By analyzing the different contributions to the overall thermal conductivity, we revealed for the first time from atomistic simulations that the vibration of the Te2− sublattice dominates the thermal transport of α-Ag2Te, while the collision between the randomly diffusing Ag+ ions and the Te2− sublattice yields a significant negative contribution to the thermal transport. We also studied the effect of isotropic compressive stain and carrier concentration on the thermal conductivity of α-Ag2Te. It has been found that the thermal conductivity can be largely reduced by applying compressive strain or with stoichiometric quantity modulation. Our studies shed light on the governing mechanism of thermal transport in ordered-disordered materials and could offer useful guidance for engineering the thermal transport properties of superionic conductors in terms of enhancing their thermoelectric performance.