Novel superstructure of the rocksalt type and element distribution in germanium tin antimony tellurides
- Department of Chemistry, Ludwig Maximilian University, Butenandtstraße 5-13, 81377 Munich (Germany)
- Institute for Mineralogy, Crystallography and Materials Science, Leipzig University, Scharnhorststraße 20, 04275 Leipzig (Germany)
- European Synchrotron Radiation Facility, CS40220, 38043 Grenoble Cedex 9 (France)
A superstructure of the rocksalt-type observed in quenched CVT-grown single crystals of Ge{sub 3.25(7)}Sn{sub 1.10(3)}Sb{sub 1.10(3)}Te{sub 6} was elucidated by X-ray diffraction using fourfold twinned crystals (space group P3{sup ¯}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-Ge{sub 3}SnSb{sub 2}Te{sub 7} (R3{sup ¯}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. - Graphical abstract: High-resolution transmission electron micrograph, SAED pattern and reciprocal lattice section of X-ray single crystal data of Ge{sub 3.25}Sn{sub 1.1}Sb{sub 1.1}Te{sub 6} with an 11P-type superstructure of the rocksalt type. - Highlights: • 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 κ{sub L}. • Resonant diffraction reveals the element distribution in 39R-Ge{sub 3}SnSb{sub 2}Te{sub 7}.
- OSTI ID:
- 22443448
- Journal Information:
- Journal of Solid State Chemistry, Vol. 219; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Insights into the Structure of the Stable and Metastable (GeTe)m(Sb2Te3)n Compounds
(GeTe){sub n}SbInTe{sub 3} (n≤3)—Element distribution and thermal behavior