Bismuth telluride
Single crystal of bismuth telluride
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Atomic structure: ideal (l) and with a twin defect (r)
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Electron micrograph of twinned bismuth telluride
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Identifiers | |
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3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.013.760 |
EC Number |
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PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
Bi2Te3 | |
Molar mass | 800.76 g·mol−1 |
Appearance | Grey powder or metallic grey crystals |
Density | 7.74 g/cm3[1] |
Melting point | 580 °C (1,076 °F; 853 K)[1] |
insoluble[1] | |
Solubility in ethanol | soluble[1] |
Structure | |
Trigonal, hR15
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R3m, No. 166[2] | |
a = 0.4395 nm, c = 3.044 nm
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Formula units (Z)
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3 |
Hazards | |
NFPA 704 (fire diamond) | |
Flash point | noncombustible[3] |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp) (pure) none (doped with selenium sulfide) [3] |
REL (Recommended)
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TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) (pure) TWA 5 mg/m3 (doped with selenium sulfide)[3] |
IDLH (Immediate danger) |
N.D. (pure and doped)[3] |
Safety data sheet (SDS) | Sigma-Aldrich |
Related compounds | |
Other anions
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Other cations
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Arsenic telluride
Antimony telluride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Bismuth telluride (Bi2Te3) is a gray powder that is a compound of
Properties as a thermoelectric material
Bismuth telluride is a
Recently, researchers have attempted to improve the efficiency of Bi2Te3-based materials by creating structures where one or more dimensions are reduced, such as nanowires or thin films. In one such instance
In another case, researchers report that bismuth telluride has high
Properties as a topological insulator
Bismuth telluride is a well-studied topological insulator. Its physical properties have been shown to change at highly reduced thicknesses, when its conducting surface states are exposed and isolated. These thin samples are obtained through either epitaxy or mechanical exfoliation.
Epitaxial growth methods such as molecular beam epitaxy and metal organic chemical vapor deposition are common methods of obtaining thin Bi2Te3 samples. The stoichiometry of samples obtained through such techniques can vary greatly between experiments, so Raman spectroscopy is often used to determine relative purity. However, thin Bi2Te3 samples are resistant to Raman spectroscopy due to their low melting point and poor heat dispersion.[9]
The crystalline structure of Bi2Te3 allows for mechanical exfoliation of thin samples by cleaving along the trigonal axis. This process is significantly lower in yield than epitaxial growth, but produces samples without defects or impurities. Similar to extracting graphene from bulk graphite samples, this is done by applying and removing adhesive tape from successively thinner samples. This procedure has been used to obtain Bi2Te3 flakes with a thickness of 1 nm.[10] However, this process can leave significant amounts of adhesive residue on a standard Si/SiO2 substrate, which in turn obscure atomic force microscopy measurements and inhibit the placement of contacts on the substrate for purposes of testing. Common cleaning techniques such as oxygen plasma, boiling acetone and isopropyl alcohol are ineffective in removing residue.[11]
Occurrence and preparation
The mineral form of Bi2Te3 is tellurobismuthite which is moderately rare.[12][13] There are many natural bismuth tellurides of different stoichiometry, as well as compounds of the Bi-Te-S-(Se) system, like Bi2Te2S (tetradymite). These bismuth tellurides are part of the tetradymite group of minerals.[14]
Bismuth telluride may be prepared simply by sealing mixed powders of bismuth and tellurium metal in a quartz tube under vacuum (critical, as an unsealed or leaking sample may explode in a furnace) and heating it to 800 °C in a muffle furnace.
See also
References
- ^ ISBN 1-4398-5511-0.
- .
- ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0056". National Institute for Occupational Safety and Health (NIOSH).
- .
- .
- S2CID 123199126.
- .
- ^ Takeiishi, M.; et al. "Thermal conductivity measurements of Bismuth Telluride thin films by using the 3 Omega method" (PDF). The 27th Japan Symposium on Thermophysical Properties, 2006, Kyoto. Archived from the original (PDF) on 2007-06-28. Retrieved 2009-06-06.
- PMID 20205455.
- S2CID 139017503.
- S2CID 38149843.
- ^ "Tellurobismuthite". Mindat.org. Retrieved November 28, 2023.
- ISSN 0369-0148.
- ^ "Tetradymite Group". Mindat.org. Retrieved November 28, 2023.