Cu2Se相变过程中弹性晶格应变的瞬时变化：异常热电性质的起因,Advanced Functional Materials

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Cu2Se相变过程中弹性晶格应变的瞬时变化：异常热电性质的起因
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2021-03-08 , DOI: 10.1002/adfm.202100431
Hui Bai _{1,

2} , Xianli Su ₁ , Dongwang Yang ₁ , Qingjie Zhang ₁ , Gangjian Tan ₁ , Ctirad Uher ₃ , Xinfeng Tang ₁ , Jinsong Wu _{1,

2}

Affiliation

超离子导体Cu ₂ Se由于其低导热性而成为有前途的热电材料。在热电参数的异常，但明显的变化已经从有序的和非立方α-Cu系的相变过程中被观察到₂硒到紊乱和立方β-Cu系₂硒。但是，这种异常变化的微观结构起源及其对热电应用的影响仍然未知。在此，通过模拟热电的实际工作条件下，从α-相变β-的Cu ₂通过原位透射电子显微镜已经仔细研究了由温度升高引起的Se。观察到，当温度升高到相变点时，Se亚晶格中会发生突然的各向异性体积变化。Cu离子的局部迁移引起的晶体体积随温度的异常变化，会引起瞬时且不常见的应变场，从而降低了载流子的迁移率并增加了电阻。Cu离子的局部迁移是导致导热系数非常低的原因。这种影响仅在相变的情况下存在。在相变过程中观察结构的热电响应可提供有关高性能热电材料开发的见识，

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An Instant Change of Elastic Lattice Strain during Cu2Se Phase Transition: Origin of Abnormal Thermoelectric Properties

The superionic conductor Cu₂Se is a promising thermoelectric material due to its low thermal conductivity. An abnormal but clear change in the thermoelectric parameters has been observed during the phase transformation from the ordered and non‐cubic α‐Cu₂Se to the disordered and cubic β‐Cu₂Se. However, the microstructural origin of the abnormal change and its implications for thermoelectric applications remain largely unknown. Herein, by mimicking the real working conditions of thermoelectrics, the phase transition from α‐ to β‐Cu₂Se induced by the rising temperature has been carefully investigated by in situ transmission electron microscopy. It is observed that an abrupt and anisotropic volume‐change in the Se‐sublattice occurs when the temperature is raised to the phase transition point. The abnormal change in the crystalline volume versus temperature, which is caused by the local migration of Cu‐ions, induces an instant and uncommon strain‐field, which reduces the carrier's mobility and increases the electrical resistance. Local migration of Cu‐ions is responsible for a quite low thermal conductivity. Such effects exist only at the instance of the phase transition. Observing the thermoelectric response of the structure during the phase transition may provide insights into the development of high performance thermoelectric materials, which fall beyond the traditional approaches.

更新日期：2021-05-17

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