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  • 1.
    Aijaz, Asim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kubart, Tomás
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Low-temperature synthesis of thermochromic vanadium dioxide thin films using reactive magnetron sputtering2015In: Abstracts, 2015Conference paper (Refereed)
  • 2.
    Aijaz, Asim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, Jose
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Low-temperature synthesis of thermochromic vanadium dioxide thin films by reactive high power impulse magnetron sputtering2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 149, p. 137-144Article in journal (Refereed)
    Abstract [en]

    Thermochromic (TC) vanadium dioxide thin films provide means for controlling solar energy throughput and can be used for energy-saving applications such as smart windows. One of the factors limiting the deployment of VO2 films in TC devices is the growth temperature tau(s). At present, temperatures in excess of 450 degrees C are required, which clearly can be an impediment especially for temperature-sensitive substrates. Here we address the issue of high tau(s) by synthesizing VO2 thin films from highly ionized fluxes of depositing species generated in high power impulse magnetron sputtering (HiPIMS) discharges. The use of ions facilitates low-temperature film growth because the energy of the depositing species can be readily manipulated by substrate bias. For comparison, films were also synthesized by pulsed direct current magnetron sputtering. Structural and optical characterization of VO2 thin films on ITO-coated glass substrates confirms previous results that HiPIMS allows tau(s) to be reduced from 500 to 300 degrees C. Importantly, we demonstrated that HiPIMS permits the composition and TC response of the films to be tuned by altering the energy of the deposition flux via substrate bias. An optimum ion energy of 100 eV was identified, which points at a potential for further reduction of tau(s) thereby opening new possibilities for industrially-relevant applications of VO2-based TC thin films. Weak TC activity was observed even at tau(s) approximate to 200 degrees C in HiPIMS-produced films.

  • 3.
    Granqvist, C.-G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bayrak Pehlivan, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Y.- X.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, S.-Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pehlivan, E.
    Marsal, R.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromics and Thermochromics for Energy Efficient Fenestration: New Applications Based on Transparent Conducting Nanoparticles2013In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Online Library, Vol. 1558, p. 12 p.-, article id mrs13-1558-z09Article in journal (Refereed)
  • 4.
    Granqvist, C.-G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bayrak Pehlivan, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Y.-X.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, S.-Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Marsal, R.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromics and Thermochromics for Energy Efficient Fenestration: New Applications Based on Transparent Conducting Nanoparticles2013In: MRS Proceedings Library, p. 1-12, article id mrs13-1558-z09Article in journal (Refereed)
  • 5.
    Granqvist, C.-G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bayrak Pehlivan, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Y.-X.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, S.-Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Transparent Conducting Nanoparticle Coatings for Energy Efficient Fenestration: Applications in Electrochromics and Thermochromics2013In: Soc. Vacuum Coaters 56th Ann. Techn. Conf. Proc., 2013Conference paper (Refereed)
  • 6.
    Granqvist, C.-G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Y.- X.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic Fenestration Based on VO2: Finally a Technology of Practical Interest?2015In: Society of Vacuum Coaters 59th Ann. Techn. Conf. Proc., Albuquerque, NM, USA: Society of Vacuum Coaters , 2015Chapter in book (Refereed)
  • 7.
    Granqvist, Claes Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yuxia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, José Amenedo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, G A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic Fenestration Based on VO2: Finally a Technology of Practical Interest?2016In: Society Of Vacuum Coaters 59th Annual Technical Conference Proceedings, 2016 / [ed] Lampert, J Marken, K, 2016, p. 62-69Conference paper (Refereed)
    Abstract [en]

    Vanadium-dioxide-based thermochromic thin films and nanoparticle composites can have significant transmittance for visible light, Tlum, while they are able to transmit more near-infrared solar radiation at τ < τc than at τ > τc, where τ denotes temperature and τc ≈ 68 °C. It has been understood for many years that these properties are of principle interest for energy efficient fenestration, but the technology has been slow to mature. The present paper summarizes the state of the art of VO2-based thermochromics and points at the many advances that have been made during recent years. Specifically, the paper discusses how to employ doping to adjust τc to room temperature and to increase Tlum, how to use nano materials to enhance the solar energy transmittance modulation and Tlum, and how to prepare nanoparticle composites by sputtering. A brief discussion is given on thermochromic light scattering, which is a recently discovered phenomenon.

  • 8.
    Granqvist, Claes-Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bayrak Pehlivan, Ilknur
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electrochromics and thermochromics for energy efficient fenestration: Functionalities based on nanoparticles of In2O3:Sn and VO22014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 559, p. 2-8Article in journal (Refereed)
    Abstract [en]

    Windows incorporating electrochromic (EC) and thermochromic (TC) materials are of great interest for today's and tomorrow's buildings and can create energy efficiency jointly with indoor comfort. This paper summarizes several recent studies and shows that nanoparticles of transparent conducting oxides-specifically In2O3: Sn (ITO) and thermochromic VO2-can lead to desirable functionalities. We consider three examples: (i) the use of ITO nanoparticles in conventional polaronic EC devices in order to suppress near-infrared solar transmittance, (ii) performance limits for plasmonic EC devices based on ITO nanoparticles, and (iii) ITO-VO2-based nanocomposites combining low thermal emittance with TC properties. We also consider Mg doping of VO2 to enhance the luminous transmittance and Al2O3/VO2 double layers with improved durability. Both experimental and theoretical results are reported. (C) 2013 Elsevier B. V. All rights reserved.

  • 9.
    Granqvist, Claes-Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Montero, José Amenedo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic vanadium-dioxide-based thin films and nanoparticles: Survey of some buildings-related advances2016In: Journal of Physics: Conference Series: INERA Conference: Vapor Phase Technologies for Metal Oxide and Carbon Nanostructures, Institute of Physics Publishing (IOPP), 2016, Vol. 764, article id 012002Conference paper (Refereed)
    Abstract [en]

    Today’s architecture uses large glazings (windows and glass facades) to obtain good indoors–outdoors contact and day-lighting. However glazings offer challenges and often lead to excessive solar energy inflow and thereby a need for energy-demanding space cooling. This paper summarizes recent work on thermochromic (TC) materials intended for energy-efficient buildings and outlines how vanadium-dioxide-based thin films and nanoparticle composites can be used in TC glazings which admit more solar energy below a comfort temperature than above this temperature, so that the cooling need is diminished, while the transmittance of visible light remains high. We also report on some very recent work on TC light scattering.

  • 10.
    Ji, Y.- X.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Boman, M.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromics for Energy Efficient Buildings: Thin Surface Coatings and Nanoparticle Composites2015In: Nano- and Biotech-Based Materials for Energy Building Efficiency / [ed] F. Pacheco-Torgal, C. Buratti, S. Kalaiselva, C.G. Granqvist, V. Ivanov, London, UK: Springer London, 2015, p. 71-96Chapter in book (Refereed)
  • 11.
    Ji, Yuxia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic VO2-based materials for smart windows: Progress towards applications in buildings2018Doctoral 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.

    List of papers
    1. Thermochromic VO2 films by thermal oxidation of vanadium in SO2
    Open this publication in new window or tab >>Thermochromic VO2 films by thermal oxidation of vanadium in SO2
    2016 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 144, p. 713-716Article in journal (Refereed) Published
    Abstract [en]

    Thermochromic films of VO2 were prepared by a two-step procedure: Sputtering was first used to deposit metallic vanadium, and such layers were subsequently oxidized in SO2 at a temperature in the 600-650 degrees C range. X-ray diffraction, Raman spectroscopy, measurements of temperature-dependent electrical resistance, and spectrophotometric transmittance data at different temperatures were employed to demonstrate that the films consisted of polycrystalline VO2 with good thermochromism, especially when oxidized at the highest temperature. Oxidation in SO2 is able to produce VO2 without the stringent process control that can be an obstacle for making VO2 by oxidation in O-2.

    Keyword
    VO2, Thermochromism, Thin film, SO2
    National Category
    Materials Engineering Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-272047 (URN)10.1016/j.solmat.2015.10.012 (DOI)000366223900091 ()
    Funder
    EU, European Research Council, 267234
    Available from: 2016-01-13 Created: 2016-01-11 Last updated: 2018-02-28Bibliographically approved
    2. Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings
    Open this publication in new window or tab >>Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings
    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.

    Keyword
    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:nbn:se:uu:diva-232663 (URN)10.1016/j.tsf.2014.03.043 (DOI)000340658100091 ()
    Projects
    EU GRINDOOR
    Funder
    EU, FP7, Seventh Framework Programme, 267234
    Available from: 2014-09-22 Created: 2014-09-22 Last updated: 2018-02-28Bibliographically approved
    3. Sputter deposition of thermochromic VO2 films on In2O3: Sn, SnO2, and glass: Structure and composition versus oxygen partial pressure
    Open this publication in new window or tab >>Sputter deposition of thermochromic VO2 films on In2O3: Sn, SnO2, and glass: Structure and composition versus oxygen partial pressure
    Show others...
    2015 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 33, no 3, p. 1-7, article id 031805Article in journal (Refereed) Published
    Abstract [en]

    Thermochromic thin films of VO2 were produced by reactive DC magnetron sputtering and were characterized by atomic force microscopy, scanning electron microscopy, x-ray diffraction, spectrophotometry, and resistance measurements. Depositions took place onto substrates of glass with and without layers of electrically conducting ITO (i.e., In2O3: Sn) and nonconducting SnO2. The substrate conditions were of large importance; thus, VO2 could be prepared on ITO within a significantly wider process window of oxygen partial pressure than for the other substrates and could yield highly granular deposits. VO2 films on ITO typically showed some lattice compression. Our results are valuable for the preparation and implementation of thermochromic glazings, which are of importance for energy efficient buildings.

    National Category
    Nano Technology
    Identifiers
    urn:nbn:se:uu:diva-256852 (URN)10.1116/1.4918714 (DOI)000355011700040 ()
    Available from: 2015-06-26 Created: 2015-06-26 Last updated: 2018-02-28Bibliographically approved
    4. TiO2/VO2 bilayer coatings for glazing: Synergetically enhanced photocatalytic, thermochromic, and luminous properties
    Open this publication in new window or tab >>TiO2/VO2 bilayer coatings for glazing: Synergetically enhanced photocatalytic, thermochromic, and luminous properties
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-343522 (URN)
    Available from: 2018-02-27 Created: 2018-02-27 Last updated: 2018-02-28
    5. Thermochromic light scattering from particulate VO2 layers
    Open this publication in new window or tab >>Thermochromic light scattering from particulate VO2 layers
    2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 8, article id 085302Article in journal (Refereed) Published
    Abstract [en]

    Particulate layers of thermochromic (TC) VO2 were made by reactive DC magnetron sputtering of vanadium onto In2O3: Sn-coated glass. The deposits were characterized by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Specular and diffuse optical transmittance and reflectance were recorded in the 300-2500-nm wavelength range and displayed pronounced TC effects. These properties could be reconciled with a semi-quantitative model based on Lorentz-Mie theory applied to the distribution of particle sizes and accounting for particle shapes by the Grenfell-Warren approach with equal-volume-to-area spheres.

    National Category
    Other Physics Topics Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-283664 (URN)10.1063/1.4942211 (DOI)000371601800048 ()
    Funder
    Swedish Research Council FormasEU, European Research Council, 267234
    Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2018-02-28Bibliographically approved
    6. Nanothermochromic VO2-SiO2 composite coating for energy-efficient glazings
    Open this publication in new window or tab >>Nanothermochromic VO2-SiO2 composite coating for energy-efficient glazings
    (English)Manuscript (preprint) (Other academic)
    National Category
    Nano Technology
    Identifiers
    urn:nbn:se:uu:diva-343521 (URN)
    Available from: 2018-02-27 Created: 2018-02-27 Last updated: 2018-02-28
  • 12.
    Ji, Yu-Xia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Durability of thermochromic VO2 thin films under heating and humidity: Effect of Al oxide top coatings2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 562, p. 568-573Article in journal (Refereed)
    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.

  • 13.
    Ji, Yu-Xia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Direct Formation of Thermochromic Composite Films of VO2 Nanoparticles in SiO2 Hosts2016In: 2016 Ieee 16th International Conference On Nanotechnology (IEEE-NANO), 2016, p. 823-825Conference paper (Refereed)
    Abstract [en]

    Vanadium dioxide (VO2) is a key material for modern thermochromic energy-efficient window coatings. Nanocomposite VO2-SiO2 films were fabricated by reactive magnetron sputtering. VO2 nanoparticles with grain sizes of about 100 nm were distributed uniformly in the SiO2 host, and the composite film showed excellent thermochromic properties with plasmonic effect.

  • 14.
    Ji, Yu-Xia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Thermochromic VO2 films by thermal oxidation of vanadium in SO22016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 144, p. 713-716Article in journal (Refereed)
    Abstract [en]

    Thermochromic films of VO2 were prepared by a two-step procedure: Sputtering was first used to deposit metallic vanadium, and such layers were subsequently oxidized in SO2 at a temperature in the 600-650 degrees C range. X-ray diffraction, Raman spectroscopy, measurements of temperature-dependent electrical resistance, and spectrophotometric transmittance data at different temperatures were employed to demonstrate that the films consisted of polycrystalline VO2 with good thermochromism, especially when oxidized at the highest temperature. Oxidation in SO2 is able to produce VO2 without the stringent process control that can be an obstacle for making VO2 by oxidation in O-2.

  • 15.
    Ji, Yu-Xia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Durability of VO 2 -based thin films at elevated temperature: Towards thermochromic fenestration2014In: INERA Workshop: Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices / Parallel session of the 18th International School on Condensed Matter Physics, 2014, p. UNSP 012005-Conference paper (Refereed)
    Abstract [en]

    An explorative study was performed on sputter-deposited thermochromic VO 2 films with top coatings of Al oxide and Al nitride. The films were exposed to dry air at a high temperature. Bare 80-nm-thick VO 2 films rapidly converted to non-thermochromic V 2 O 5 under the chosen conditions. Al oxide top coatings protected the underlying VO 2 films and, expectedly, increased film thickness yielded improved protection. Specifically, it was found that a 30-nm-thick sputter-deposited Al oxide top coating delayed the oxidation by more than one day upon heating at 300°C. The results demonstrate the importance of protective layers in thermochromic windows for practical application.

  • 16.
    Montero, Jose
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Li, Shu-Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sputter deposition of thermochromic VO2 films on In2O3: Sn, SnO2, and glass: Structure and composition versus oxygen partial pressure2015In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 33, no 3, p. 1-7, article id 031805Article in journal (Refereed)
    Abstract [en]

    Thermochromic thin films of VO2 were produced by reactive DC magnetron sputtering and were characterized by atomic force microscopy, scanning electron microscopy, x-ray diffraction, spectrophotometry, and resistance measurements. Depositions took place onto substrates of glass with and without layers of electrically conducting ITO (i.e., In2O3: Sn) and nonconducting SnO2. The substrate conditions were of large importance; thus, VO2 could be prepared on ITO within a significantly wider process window of oxygen partial pressure than for the other substrates and could yield highly granular deposits. VO2 films on ITO typically showed some lattice compression. Our results are valuable for the preparation and implementation of thermochromic glazings, which are of importance for energy efficient buildings.

  • 17.
    Montero, José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu-Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thermochromic light scattering from particulate VO2 layers2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 8, article id 085302Article in journal (Refereed)
    Abstract [en]

    Particulate layers of thermochromic (TC) VO2 were made by reactive DC magnetron sputtering of vanadium onto In2O3: Sn-coated glass. The deposits were characterized by scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Specular and diffuse optical transmittance and reflectance were recorded in the 300-2500-nm wavelength range and displayed pronounced TC effects. These properties could be reconciled with a semi-quantitative model based on Lorentz-Mie theory applied to the distribution of particle sizes and accounting for particle shapes by the Grenfell-Warren approach with equal-volume-to-area spheres.

  • 18.
    Yu-Xia, Ji
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Shu-Yi, Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnar A., Niklasson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Claes-Göran, Granqvist
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Effect of Al oxide top coatings on the durability of thermochromic VO2thin films2014Conference paper (Other academic)
1 - 18 of 18
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