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- Granqvist, Claes-Göran, et al.
(författare)
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Towards the smart window : progress in electrochromics
- 1997
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Ingår i: Journal of Non-Crystalline Solids. - 0022-3093 .- 1873-4812. ; 218, s. 273-279
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic devices have the ability to produce reversible and persistent changes of their optical properties. The phenomenon is associated with joint ion and electron transport into/out of an electrochromic thin film, in most cases being a transition metal oxide. This paper outlines the various applications of such devices in smart windows suitable for energy-conscious architecture, in variable-reflectance mirrors, and in display devices. Critical materials issues and design concepts are discussed. The paper also covers two specific research topics: computed electronic structure of crystalline WO3 incorporating ionic species, showing how reflectance modulation emerges from a first-principles calculation; and Li+ dynamics in heavily disordered Ti oxide, illustrating how diffusion constants derived from impedance spectroscopy can be reconciled with the Anderson—Stuart model.
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| 4. |
- Isidorsson, Jan
(författare)
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Lithium intercalation in tin oxide films : Physics and electrochemistry
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tin oxide films were made by reactive rf magnetron sputtering under conditions that led to both electronic and ionic conductivity. It was found that a high sputter pressure promoted porosity and a high charge capacity. The film structure was studied by X-ray diffraction, atomic force microscopy , spectroscopic light scattering, and Rutherford back scattering . The effect of lithium intercalation on the optical constants was studied with spectrophotometry and ellipsometry, and the distribution of the lithium ions was investigated with nuclear reaction analysis, The concentration of lithium was highest at the surface, and decreased further into the film. Lithium intercalation produced electrochromism with coloration efficiency peaked in the infrared. Fluorine doping, or mixtures with cerium, resulted in a decreased charge capacity.Chronopotentiometry, chronoamperometry and cyclic voltammetry were used to investigate the electrochemical properties of the tin oxide electrodes. Charge/discharge curves as well as potential step techniques were used to interpret phase formation and transformations and to study the dynamics of these reactions. The diffusion coefficient was ~10-11 cm2/s, slightly decreasing with decreasing potential. Cyclic voltammograms were interpreted in terms of a fractal dimension of a self-similar surface relief. Excellent agreement was found with the fractal dimension obtained with atomic force microscopy. Impedance spectra were taken for a wide range of frequencies and polarising voltages. Nyqvist diagrams were interpreted from a circuit model with elements representing Li+ insertion at the electrolyte/film interface and electron insertion at the film/substrate interface.Mössbauer spectroscopy was used to determine the valence state of the Sn-atoms; a change from Sn4+ to Sn2+ was detected after electrochemical intercalation of Li+. Three different effects of charging were identified: double-layer charging at low levels, valence change at medium levels, and deposition on the surface at high levels. A novel in situ light scattering experiment was developed to study the latter phenomenom.
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| 6. |
- Isidorsson, Jan, et al.
(författare)
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Physical and Electrochemical properties of Li-intercalated Sn oxide films made by sputtering
- 1995
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Ingår i: Ionics (Kiel). - 0947-7047 .- 1862-0760. ; 1:5-6, s. 400-405
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Tidskriftsartikel (refereegranskat)abstract
- Sn oxide films were made by reactive rf magnetron sputtering under conditions that led to both electronic and ionic conductivity. The film structure was studied by X-ray diffraction and Atomic Force Microscopy (AFM). Li+ intercalation produced electrochromism with coloration efficiency peaked in the infrared. Cyclic voltammograms taken at different sweep rates were interpreted in terms of a unique structural parameter related to the fractal dimension of a self-affine surface relief and in excellent agreement with the fractal dimension as obtained with AFM. Mössbauer spectroscopy was used to determine the valence state of the Sn-atoms; a change from Sn4+ to Sn2+ was detected after electrochemical intercalation of Li+.
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| 7. |
- Strömme, Maria, et al.
(författare)
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Impedance studies on Li insertion electrodes of Sn oxide and oxyfluoride
- 1996
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 80:1, s. 233-241
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Tidskriftsartikel (refereegranskat)abstract
- Films of Sn oxide and oxyfluoride were made by reactive rf magnetron sputtering onto ITO‐coated glass. We analyzed the composition by Rutherford backscattering spectrometry, the structure by x‐ray diffraction, and the surfacetopography by atomic force microscopy. Li intercalation from a liquid electrolyte was more facile in the oxide than in the oxyfluoride, as found from cyclic voltammetry. Impedance spectra were taken for a wide range of frequencies and polarizing voltages. Nyqvist diagrams were interpreted from a circuit model with elements representing Li insertion at the electrolyte/film interface and electron insertion at the film/ITO interface. The data were consistent with a fractal surface of the Sn oxide film, with a dimension in excellent agreement with measures obtained through several independent techniques. The chemical diffusion coefficient was ∼10−13 cm2/s and slightly decreasing with increasing potential for all films.
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