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Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.ORCID iD: 0000-0002-8279-5163
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2014 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 562, p. 568-573Article in journal (Refereed) Published
Abstract [en]

An explorative study was performed on sputter-deposited thermochromic (TC) VO2 films exposed to heat treatment under dry and humid conditions. The ambient conditions were harsh and 80-nm-thick VO2 films were rapidly converted to non-TC V2O5. It was found that a 30-nm-thick sputter-deposited Al oxide top coating provided good protection and delayed the oxidation for more than one day upon heating in dry air at 300 degrees C and that protection occurred for several days at 95% relative humidity and 60 degrees C. The thickness of the Al oxide was important and, expectedly, increased thickness yielded enhanced protection. Our results are important for TC fenestration as well as for other technical applications.

Place, publisher, year, edition, pages
2014. Vol. 562, p. 568-573
Keywords [en]
Thermochromism, Vanadium dioxide, Durability, Relative humidity, Aluminum oxide
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-232663DOI: 10.1016/j.tsf.2014.03.043ISI: 000340658100091OAI: oai:DiVA.org:uu-232663DiVA, id: diva2:749026
Projects
EU GRINDOOR
Funder
EU, FP7, Seventh Framework Programme, 267234Available from: 2014-09-22 Created: 2014-09-22 Last updated: 2018-02-28Bibliographically approved
In thesis
1. Thermochromic VO2-based materials for smart windows: Progress towards applications in buildings
Open this publication in new window or tab >>Thermochromic VO2-based materials for smart windows: Progress towards applications in buildings
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vanadium dioxide is a well-known thermochromic material, whose optical properties can be varied reversibly in response to fluctuation of temperature. It is attractive in various fields due to its unique properties as well as its prospective applications. Especially, it is the most favorite candidate for smart window applications which can significantly lower energy consumption. Ideally, VO2-based thermochromic windows can regulate solar radiation gain dynamically according to the exterior environment conditions. However, commercial utilization of VO2 thermochromic windows is still on the way. There are still a few issues needed to be overcome, such as high phase transition temperature, the unfavorable yellow-brown color, low luminous transmittance and weak solar energy modulation ability.

Vanadium oxides are known to have rich polymorphs and devices using thermochromic effect often require absence of impurities, so that stringent process control is crucial for practical manufacturing of VO2 materials. In this work, a novel route for fabrication of VO2 thin films was developed thermodynamically and verified experimentally. Another concern related to VO2-based materials is the relatively short durability of their desirable properties as VO2 is not the most thermodynamic stable species. Hence the lifetimes of the thermochromic VO2 films under various environmental conditions were evaluated. Furthermore, studies have been made to investigate the impacts of substrates on VO2 film growth.

For window coating applications, the light scattering is of importance. Therefore, the light scattering effect for particulate VO2 film was studied. Additionally, the low luminous transmittance of VO2 film can be substantially increased by use of a top coating with suitable refractive index. In our study a TiO2 top layer was used, which leads to improved thermochromic behavior. Moreover, incorporation of VO2 plasmonic pigments into a matrix is a useful way to overcome the unsatisfied thermochromic performance of conventional VO2 films. A composite film of VO2-SiO2 was fabricated and its optical properties were studied. Besides, phase-pure VO2 nanospheres were synthesized via chemical route and their thermochromic properties were investigated.

In general, these studies promote development and progress of VO2-based material further to be used in heat and light regulation applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 107
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1639
Keywords
Thermochromic, Vanadium dioxide, Smart windows
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-343524 (URN)978-91-513-0255-3 (ISBN)
Public defence
2018-04-20, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2018-03-27 Created: 2018-02-28 Last updated: 2018-04-24

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Ji, Yu-XiaLi, Shu-YiNiklasson, Gunnar A.Granqvist, Claes-Göran

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