Structural studies of the metal-rich region in the ternary Ta-Nb-S system
Six new solid solution type compounds have been prepared using high temperature techniques and characterized by means of single crystal x-ray techniques during a study of the metal-rich region of the ternary Ta-Nb-S system. The structures of Nb{sub x}Ta{sub 11-x}S{sub 4} are reminiscent of niobium-rich sulfides, rather than of tantalum-rich sulfides. The coordinations of sulfur are capped trigonal prismatic while the metal coordinations are capped distorted cubic prismatic for Nb{sub x}Ta{sub 11-x}S{sub 4}, and capped distorted cubic prismatic and pentagonal prismatic for Nb{sub 12-x}Ta{sub x}S{sub 4}. The structures of Nb{sub x}Ta{sub 5-x}S{sub 2} contain homoatomic layers sequenced S-M3-M2-M1-M2-M3-S (M is mixed Nb, Ta) generating six-layer sheets, respectively. Weak S-S interactions at 3.26 and 3.19{Angstrom} between sheets contrast with the M-M binding within and between the sheets in these two novel layered compounds. The former are presumably responsible for the observed graphitic slippage of the samples. Nb{sub 21-x}Ta{sub x}S{sub 8} and Nb{sub x}Ta{sub 2-x}S are isostructural with Nb{sub 21}S{sub 8} and Ta{sub 2}S, respectively. Extended Hueckel band calculations were carried out for two layered compounds, Nb{sub x}Ta{sub 5-x}S{sub 2} (x {approx} 1.72) and Nb{sub x}ta{sub 2-x}S (x {approx} 0.95). Based upon band calculations metallic properties can be expected for these two layered compounds. The relative preference of the metal sites for the two metal elements (Ta, Nb) in two layered compounds is explained by the results of the band calculations. 17 figs., 31 tabs., 80 refs.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5053308
- Report Number(s):
- IS-T-1503; ON: DE92001766
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
NIOBIUM SULFIDES
CHEMICAL PREPARATION
SULFIDES
STRUCTURAL CHEMICAL ANALYSIS
TANTALUM SULFIDES
BOND LENGTHS
MOLECULAR ORBITAL METHOD
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION
CHALCOGENIDES
COHERENT SCATTERING
DIFFRACTION
DIMENSIONS
LENGTH
NIOBIUM COMPOUNDS
REFRACTORY METAL COMPOUNDS
SCATTERING
SULFUR COMPOUNDS
SYNTHESIS
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
360602 - Other Materials- Structure & Phase Studies