کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1330163 | 1500097 | 2014 | 10 صفحه PDF | دانلود رایگان |
• A novel superstructure of the rocksalt-type in the system Ge–Sn–Sb–Te is elucidated.
• It combines the cubic stacking of the HT phase with building blocks of the RT phase.
• It indicates the ordering mechanism during the phase transition of GST materials.
• A hierarchical structure motif is promising with respect to the reduction of κL.
• Resonant diffraction reveals the element distribution in 39R-Ge3SnSb2Te7.
A superstructure of the rocksalt-type observed in quenched CVT-grown single crystals of Ge3.25(7)Sn1.10(3)Sb1.10(3)Te6 was elucidated by X-ray diffraction using fourfold twinned crystals (space group P3¯m1, a=4.280(1) Å, c=20.966(3) Å). The structure is built up of distorted rocksalt-type building blocks typical for long-range ordered GST materials and substitution variants thereof. In contrast to those phases, an exclusive ABC-type cubic stacking sequence of the Te-atom layers is present. High-resolution electron microscopy reveals spheroidal domains with this structure (average diameter 25 nm) whose stacking direction is perpendicular to the 〈1 1 1〉 directions of the basic rocksalt-type structure. Additional slab-like domains with a lateral extension up to 1 µm occasionally result in a hierarchical structure motif. Due to the similar electron counts of the elements involved, resonant diffraction was used in order to elucidate the element distribution in rocksalt-type building blocks of the stable layered compound 39R-Ge3SnSb2Te7 (R3¯m, a=4.24990(4) Å, c=73.4677(9) Å). Sb tends to occupy the atom site close to the van der Waals gaps while Ge concentrates in the center of the building blocks.
High-resolution transmission electron micrograph, SAED pattern and reciprocal lattice section of X-ray single crystal data of Ge3.25Sn1.1Sb1.1Te6 with an 11P-type superstructure of the rocksalt type.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 219, November 2014, Pages 108–117