Vanadium(IV) oxide
Names | |
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IUPAC name
Vanadium(IV) oxide
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Other names
Vanadium dioxide
Divanadium tetroxide | |
Identifiers | |
3D model (
JSmol ) |
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ChEBI | |
ChemSpider | |
ECHA InfoCard
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100.031.661 |
EC Number |
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873472 | |
PubChem CID
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CompTox Dashboard (EPA)
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Properties | |
VO2 | |
Molar mass | 82.94 g/mol |
Appearance | Blue-black powder |
Density | 4.571 g/cm3 (monoclinic) 4.653 g/cm3 (tetragonal) |
Melting point | 1,967 °C (2,240 K)[1] |
+99.0·10−6 cm3/mol[2] | |
Structure | |
Distorted rutile (<70 °C (343 K), monoclinic) Rutile (>70 °C (343 K), tetragonal) | |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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toxic |
GHS labelling:[3] | |
Warning | |
H315, H319 | |
P264, P280, P302+P352, P305+P351+P338, P332+P313, P337+P313, P362 | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
Related compounds | |
Other anions
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Vanadium disulfide Vanadium diselenide Vanadium ditelluride |
Other cations
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Niobium(IV) oxide
Tantalum(IV) oxide |
Vanadium(II) oxide Vanadium(III) oxide Vanadium(V) oxide | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Vanadium(IV) oxide or vanadium dioxide is an
Properties
Structure
At temperatures below Tc = 340 K (67 °C), VO
2 has a
2. In the monoclinic phase, the V4+ ions form pairs along the c axis, leading to alternate short and long V-V distances of 2.65 Å and 3.12 Å. In comparison, in the rutile phase the V4+ ions are separated by a fixed distance of 2.96 Å. As a result, the number of V4+ ions in the crystallographic unit cell doubles from the rutile to the monoclinic phase.[5]
The equilibrium morphology of rutile VO
2 particles is acicular, laterally confined by (110) surfaces, which are the most stable termination planes.[16] The surface tends to be oxidized with respect to the stoichiometric composition, with the oxygen adsorbed on the (110) surface forming vanadyl species.[16] The presence of V5+ ions at the surface of VO
2 films has been confirmed by X-ray photoelectron spectroscopy.[17]
Memory effect
In 2022, a to date unique and unknown feature of the material was reported – it can "remember" previous external stimuli[
Electronic
At the rutile to monoclinic transition temperature (67 °C (340 K)), VO
2 also exhibits a metal to
Thermal
Metallic VO2 contradicts the
Potential applications include converting waste heat from engines and appliances into electricity,[24] and windows or window coverings that keep buildings cool.[12] Thermal conductivity varied when VO2 was mixed with other materials. At a low temperature it could act as an insulator, while conducting heat at a higher temperature.[22]
Synthesis and structure
Following the method described by
- V
2O
5 + V
2O
3 → 4 VO
2
At room temperature VO2 has a distorted
Infrared reflectance
VO
2 expresses temperature-dependent reflective properties. When heated from room temperature to 80 °C (353 K), the material's thermal radiation rises normally until 74 °C (347 K), before suddenly appearing to drop to around 20 °C (293 K). At room temperature, VO
2 is almost transparent to infrared light. As its temperature rises it gradually changes to reflective. At intermediate temperatures it behaves as a highly absorbing dielectric.[31][32]
A thin film of vanadium oxide on a highly reflecting substrate (for specific infrared wavelengths) such as sapphire is either absorbing or reflecting, dependent on temperature. Its emissivity varies considerably with temperature. When the vanadium oxide transitions with increased temperature, the structure undergoes a sudden decrease in emissivity – looking colder to infrared cameras than it really is.[33][31]
Varying the substrate materials (e.g., to indium tin oxide), as well as modifying the vanadium oxide coating using doping, straining, or other processes, alters the wavelengths and temperature ranges at which the thermal effects are observed.[31][33]
Nanoscale structures that appear naturally in the materials' transition region can suppress thermal radiation as the temperature rises. Doping the coating with tungsten lowers the effect's thermal range to room temperature.[31]
Uses
Infrared radiation management
Undoped and tungsten-doped vanadium dioxide films can act as "spectrally-selective" coatings to block infrared transmission and reduce the loss of building interior heat through windows.[33][34][35] Varying the amount of tungsten allows regulating the phase transition temperature at a rate of 20 °C (20 K) per 1 atomic percent of tungsten.[33] The coating has a slight yellow-green color.[36] The performance of energy-saving smart windows can be enhanced by combining VO2 with antireflection layers.[37] The technology of low-temperature preparation of V1-xWxO2-based multilayers has been scaled up to industrial dimensions.[38]
Other potential applications of its thermal properties include passive camouflage, thermal beacons, communication, or to deliberately speed up or slow down cooling. These applications could be useful for a variety of structures from homes to satellites.[31]
Vanadium dioxide can act as extremely fast
Passive radiative cooling
Vanadium dioxide is essential to achieving temperature-based 'switchable' cooling and heating effects for passive daytime radiative cooling surfaces without additional energy input. Temperature-based switching can be essential to mitigate potential "overcooling" effects of radiative cooling devices in urban environments, especially those with hot summers and cool winters, making it possible for radiative coolers to also function as passive heating devices when necessary.[40][41]
Phase change computing and memory
The insulator-metal phase transition in VO2 can be manipulated at the nanoscale using a biased conducting atomic force microscope tip,[42] suggesting applications in computing and information storage.[10]
See also
References
- ^ Haynes, p. 4.98
- ^ Haynes, p. 4.136
- ^ "Vanadium dioxide". pubchem.ncbi.nlm.nih.gov.
- ^ ISBN 978-0-08-022057-4.
- ^ .
- PMID 23546301.
- S2CID 205238368.
- S2CID 7107273.
- S2CID 95830675.
- ^ S2CID 11347598.
- ^ "Phase-Change Materials and Switches for Enabling Beyond-CMOS Energy Efficient Applications". Phase-Change Switch Project. Retrieved 2018-05-05.
- ^ . Retrieved 15 July 2022.
- S2CID 245263196.
- S2CID 245262692.
- ^ Barraud, Emmanuel (2018-02-05). "A revolutionary material for aerospace and neuromorphic computing". EPFL News. Retrieved 2018-05-05.
- ^ S2CID 29006673.
- .
- Ecole Polytechnique Federale de Lausanne. Retrieved 15 September 2022.
- S2CID 251759964.
- .
- PMID 9994356.
- ^ a b MacDonald, Fiona (2017-01-28). "Physicists Have Found a Metal That Conducts Electricity but Not Heat". ScienceAlert.
- S2CID 206650639.
- ^ "Scientists discover material that conducts electricity but no heat". The Indian Express. 29 January 2017. Retrieved 29 July 2022.
- ^ Brauer, G. ed. (1963) Handbook of Preparative Inorganic Chemistry, 2nd Ed. Academic Press. NY. Vol. 1. p. 1267.
- ^ New studies explain insulator-to-metal transition of vanadium dioxide, PhysOrg. April 11, 2015.
- PMID 27877369.
- hdl:2346/95263.
- .
- ^ a b c d e "Natural metamaterial looks cooler when heated". physicsworld.com. 2013-10-25. Retrieved 2014-01-01.
- S2CID 53496680.
- ^ PMID 28970866.
- ^ Guzman, G. Vanadium dioxide as infrared active coating. solgel.com
- ^ "Intelligent Window Coatings that Allow Light In but Keep Heat Out - News Item". Azom.com. 2004-08-12. Retrieved 2012-09-12.
- ^ Espinasse, Phillip (2009-11-03). "Intelligent Window Coating Reflects Heat, Not Light". oe magazine. Archived from the original on 2005-05-24. Retrieved 2012-09-12.
- S2CID 247568375.
- S2CID 247121490.
- ^ "Timing nature's fastest optical shutter". Physorg.com. 2005-04-07.
- S2CID 240331557.
- ^ Wang, Zhaochen; Kim, Sun-Kyung; Hu, Run (March 2022). "Self-switchable radiative cooling". Matter. 5 (3) – via Elsevier Science Direct.
- S2CID 122696544.
Bibliography
- Haynes, William M., ed. (2011). ISBN 978-1-4398-5511-9.