Temperature-dependent ordering phenomena in single crystals of germanium antimony tellurides
Temperature-dependent ordering phenomena in single crystals of germanium antimony tellurides
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DOI：
10.1016/j.jssc.2015.04.007
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发表时间：
2015-07
影响因子：
3.3
通讯作者：
P. Urban;M. Schneider;O. Oeckler
中科院分区：
文献类型：
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作者：
P. Urban;M. Schneider;O. Oeckler
用半定量的X射线散射模型研究了淬冷单晶（GeTe）nSb 2 Te 3（n~ 2.8，n ~5，n ~11）的温度依赖行为.在室温下的结构表现出三角形的孪晶域，每个包含一个堆叠无序序列的扭曲岩盐型板与可变厚度。Ge和Sb共享阳离子位置，空位在板之间的缺陷层（货车范德华能隙）中部分有序。用共振衍射数据确定的平均结构对应于岩盐型结构，其阳离子位置沿堆叠方向沿着分裂。在加热时，阳离子有序化导致在~400 °C下的岩盐型亚稳超结构，其在~500 °C下转变为具有随机分布的阳离子和空位的岩盐型高温相;这种结构也使用共振衍射进行了细化。以高或中等速率冷却不会产生长程有序相，而是直接导致孪晶无序相。
The temperature-dependent behavior of quenched single-crystalline (GeTe)nSb2Te3(n~2.8,n~5 andn~11) was investigated by semiquantitative modeling of diffuse X-ray scattering. The structure at room temperature exhibits trigonal twin domains, each comprising a stacking-disordered sequence of distorted rocksalt-type slabs with variable thicknesses. Ge and Sb share the cation position and vacancies are partially ordered in defect layers (van der Waals gaps) between the slabs. The average structure determined with resonant diffraction data corresponds to a rocksalt-type structure whose cation position is split along the stacking direction. Upon heating, cation ordering leads to a metastable superstructure of the rocksalt type at ~400 °C, which transforms to a rocksalt-type high-temperature phase with randomly distributed cations and vacancies at ~500 °C; this structure was also refined using resonant diffraction. Cooling at high or intermediate rates does not yield the long-range ordered phase, but directly leads to the twinned disordered phase.