Structure and electrical transport properties of the misfit-layer compound (BiS)1.08TaS2
| Autor: | J. Wulff, J. L. de Boer, R.J. Haange, Auke Meetsma, Ga Wiegers |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
chemistry.chemical_classification
Stereochemistry Mechanical Engineering Metals and Alloys Crystal structure Condensed Matter Physics Electronic Optical and Magnetic Materials Crystallography chemistry Mechanics of Materials Electrical resistivity and conductivity Hall effect Seebeck coefficient X-ray crystallography Materials Chemistry Orthorhombic crystal system Inorganic compound Single crystal |
| Zdroj: | Synthetic Metals. 39:1-12 |
| ISSN: | 0379-6779 |
| DOI: | 10.1016/0379-6779(90)90194-p |
| Popis: | (BiS) 1.08 TaS 2 , formerly designated as ‘BiTaS 3 ’, has been found by single-crystal X-ray diffraction to be a misfit-layer compound built of alternate TaS 2 sandwiches as also present in 2H-TaS 2 and modified double layers of BiS, structurally based upon (hypothetical) NaCl-type BiS. The BiS part of the structure shows a face-centered (f.c.) orthorhombic unit cell with dimensions a 1 =6.101(1) A , b 1 =5.724(1) A , c 1 =23.066(8) A and Z=8 for reflections with h , k and l even, but for k odd of the f.c. cell a very complex pattern of satellites around the extinct main reflections is observed. The TaS 2 part of the structure has unit cell dimensions: a 2 = 3.300(1) A , b 2 = 5.727(3) A , c 2 = 23.12(1) A , space group Fm2m and Z = 4. Refinements of single crystal data ( R F = 0.033 for 438 reflections) confirmed the presence of TaS 2 sandwiches, the TaS distances being 2.524(4) A (×2) and 2.443(3) A (×4). The complex structure of the BiS subsystem was not solved, but the Okl reflections ( R F =0.058 for 114 reflections) showed the BiS structure to be a modulation along [100] of a double-layer structure as observed for other misfit-layer compounds. The BiS distances, calculated for an undistorted structure, indicate that Bi in the BiS part is on average Bi 2+ . The electrical conduction is by light holes (the Hall constant being positive) and heavy electrons (negative sign of the Seebeck coefficient) presumably in the 5d z 2 conduction band of the TaS 2 part. There is no substantial electron donation from the BiS to the TaS 2 part, therefore Bi is Bi 2+ , in agreement with the BiS distances. |
| Databáze: | OpenAIRE |
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