Nano-scale compositional oscillation and phase intergrowth in Cu2S0.5Se0.5 and their role in thermal transport
Nano-scale compositional oscillation and phase intergrowth in Cu2S0.5Se0.5 and their role in thermal transport
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DOI：
10.1016/j.jmst.2020.10.077
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发表时间：
2021-07
影响因子：
10.9
通讯作者：
Yuyu Wei;P. Lu;Chenxi Zhu;K. Zhao;Xun Shi;Lidong Chen;Fangfang Xu
中科院分区：
文献类型：
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作者：
Yuyu Wei;P. Lu;Chenxi Zhu;K. Zhao;Xun Shi;Lidong Chen;Fangfang Xu
固溶体合金化是一种很有前途的建立高性能热电材料的方法。通过合金化不同的元素，相结构和相组成可能会发生变化，并伴随着各种有趣的微观结构的出现，包括质量波动、晶格应变、纳米级缺陷和spinodal分解，所有这些都可能极大地影响材料的电输运，特别是热输运。本研究利用原子分辨电子显微镜对cu2s0.5 se0.5固溶体的原子结构进行了研究，以探讨该固溶体中异常热输运的结构相关物理意义。然后观察到异常生长的纳米结构。固溶体由两种高度对称的相组成，即六方相和立方相，它们交替生长，形成纳米级甚至单位胞级的高度定向的超薄片层。合金化过程中Se/S原子比的成分振荡是导致相稳定性和纳米结构互长的主要原因。独特的二相互生纳米结构使其晶格导热系数极低，与玻璃相当，声子平均自由程极短，仅为1.04 Å，具有特殊的连续六边形到立方结构的转变，且没有临界转变温度，其热特性随温度的异常变化。本研究进一步唤起了通过合金化来定制纳米结构以改善热电性能的无限可能性和潜力。
Solid solution alloying is a promising strategy to establish high performance thermoelectrics. By alloying different elements, phase structures and phase compositions may vary accompanied by appearance of variety of interesting microstructures including mass fluctuation, lattice strain, nano-scale defects and spinodal decomposition, all of which may greatly influence the electrical and specifically the thermal transport of the material. In the present study, atomic structures of Cu2S0.5Se0.5solid solution have been examined by using atom-resolved electron microscopy in order to investigate the structure-correlated physical insights for the abnormal thermal transport in this solid solution. Then the exceptional intergrowth nanostructures were observed. The solid solution consists of two high symmetrical phases, i.e. the hexagonal and cubic phase, which alternately intergrow to form highly oriented ultra-thin lamellae of nano or even, unit cell scales. The compositional oscillation in Se/S atomic ratio during alloying is responsible for the phase stability and intergrowth nanostructures. The unique binary phase intergrowth nanostructures make great contribution to the ultra-low lattice thermal conductivity comparable to glass and extremely short phonon mean free path of only 1.04 Å, peculiar continuous hexagonal-to-cubic structural transformation without a critical transition temperature and its corresponding abnormal changes of thermal characters with temperatures. The present study further evokes the unlimited possibilities and potentials for tailoring nanostructures by alloying for improved thermoelectric performance.