Ge{sub x}NbSe{sub 2} and Ge{sub x}NbS{sub 2} intercalation compounds
- Faculte de Chimie, Laboratoire Sciences des Materiaux, USTHB, BP32 El-Alia 16111 Bab-Ezzouar, 16000 Alger (Algeria)
- Centro de Microscopia Electronica, Universidad Complutense, 28040 Madrid (Spain)
The structures of two intercalation compounds, Ge{sub {approx}0.2}NbSe{sub 2} and Ge{sub {approx}0.3}NbS{sub 2} were investigated by single crystal X-ray diffraction and electron microscopy (selected area electron diffraction (SAED), high resolution electron microscopy (HRTEM) and X-ray microanalysis by energy dispersive spectroscopy (XEDS)). Crystal structure determinations of the average structure of the intercalation compounds 2H-Ge{sub 0.217}NbSe{sub 2} and 4H-Ge{sub 0.288}NbS{sub 2} are reported: the selenide compound crystallizes in the space group P6{sub 3}/mmc with a = 3.4560(9) A and c = 12.966(3) A and adopts the 2H-NbSe{sub 2} structure-type, while the sulfide compound crystallizes in the P6{sub 3}mc space group, with a = 3.3392(9) A and c = 25.404(7) A with a structure-type 4H{sub c}-NbS{sub 2} which it is known for TaSe{sub 2}. In both structures the germanium atoms are located in the empty octahedral positions of the van der Waals gap between the NbX{sub 2} (X = S, Se) layers. Electron diffraction patterns from several Ge{sub x}NbSe{sub 2} crystal flakes show different superstructures and exhibit diffracted diffuse intensity: weak satellites corresponding to a{sub 0}{radical}(3)xa{sub 0}{radical}(3) and 2a{sub 0} x 2a{sub 0} superstructures were observed for x {approx} 0.15 (a{sub 0} is the basal lattice parameter of the host structure). For x {approx} 0.25-0.33, the same type of satellite is observed with a stronger intensity. For x {approx} 0.5 only satellites corresponding to the a{sub 0}{radical}(3)xa{sub 0}{radical}(3) superstructure were present. In the case of Ge{sub x}NbS{sub 2}, with 0.10 < x < 0.25, the germanium atoms are ordered in domains with an a{sub 0}{radical}(3)xa{sub 0}{radical}(3) superstructure. In some crystals disorder along the c-axis has been observed.
- OSTI ID:
- 22029816
- Journal Information:
- Materials Research Bulletin, Vol. 44, Issue 7; Other Information: Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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