The order-disorder transition in Cu2Se and medium-range ordering in the high-temperature phase.
The order-disorder transition in Cu2Se and medium-range ordering in the high-temperature phase.
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DOI：
10.1107/s2052520620002164
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
P. Lu;Wujie Qiu;Yuyu Wei;Chenxi Zhu;Xun Shi;Lidong Chen;Fangfang Xu
中科院分区：
文献类型：
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作者：
P. Lu;Wujie Qiu;Yuyu Wei;Chenxi Zhu;Xun Shi;Lidong Chen;Fangfang Xu
硒化亚铜（Cu 2Se）的高热电性能源于其由两个独立的亚晶格组成的特殊结构，即刚性面心立方（f.c.c.）Se亚晶格和灵活的Cu亚晶格在许多间隙位置显示出各种有序的配置。当温度升高时，Cu亚晶格经历有序到无序的转变，但结构演化的细节尚未完全阐明。在这里，原位透射电子显微镜（TEM）是用来调查热诱导结构变化的Cu 2 Se在真实的和倒易空间。发现有序-无序转变在纳米块体中进行，并伴随着低温相和高温相之间的结构波动。电子衍射揭示了出现的中程有序的Cu原子在高温f.c.c.相位参照库仑相互作用的计算，构造了中程有序的超结构。这种中程原子有序持续在一个很宽的温度范围内（从相变温度超过800 K的TEM），但逐渐改变为短程有序的漫散射环的外观所示。
The high thermoelectric performance of cuprous selenide (Cu2Se) arises from its specific structures consisting of two independent sublattices, i.e. the rigid face-centered cubic (f.c.c.) Se sublattice and the flexible Cu sublattice showing a variety of ordered configurations at numerous interstitial sites. Upon increasing the temperature, the Cu sublattice undergoes an order-to-disorder transition but the details of the structural evolution have not been fully elucidated. Here, in situ transmission electron microscopy (TEM) is used to investigate the thermally induced structural changes of Cu2Se in both real and reciprocal spaces. Order-disorder transition was found to proceed in nanoblocks accompanied by the structural fluctuations between low-temperature and high-temperature phases. Electron diffraction revealed the emergence of medium-range ordering of Cu atoms in the high-temperature f.c.c. phase. By referring to the Coulomb interaction evaluations, the superstructures for the medium-range ordering were constructed. Such medium-range atomic ordering was sustained over a wide temperature range (from the phase transition temperature to over 800 K in the TEM) but gradually changed to short-range ordering as indicated by the appearance of diffuse scattering rings.