Deepa, M. and Joshi, A. G. and Srivastava , A. K. and Shivaprasad, S. M. and Agnihotry, S. A. (2006) Electrochromic nanostructured tungsten oxide films by sol-gel: Structure and intercalation properties. Journal of The Electrochemical Society, 153 (5). C365-C376. ISSN 1945-7111 (Unpublished)

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As-deposited sol-gel derived amorphous tungsten oxide films transform into nanostructured films with an interconnected framework of grains and pores and a dominant triclinic crystalline phase upon annealing at 250 degrees C. Transmission electron microscopy and scanning electron microscopy images clearly reveal the annealing-induced microstructural evolution for the film. Subsequent to lithium intercalation, the film annealed at 250 degrees C shows quasi-reversible structural changes, as ascertained by X-ray diffraction and Fourier transform infrared spectral data. Dynamic transmission modulation for film revealed a high optical modulation of 72% (gimel=650nm) and a coloration efficiency maximum of 132 cm(2) C-1 at 800 nm under a lithium intercalation level of x = 0.20. X-ray photoelectron spectroscopy of the W 4f core levels demonstrated a progressive increase in the W5+ content at the expense of W6+ proportion as the insertion coefficient was raised from 0 to 0.25, with 0.20 as the threshold value above which the W5+ content exceeds the W6+ proportion. A new W4+ state also appears which acts to lower the coloration efficiency for x >= 0.22. The presence of charged oxygen interstitials in the vicinity of electrochemically active tungsten sites is also responsible for the coloration efficiency decline at high ion insertion levels.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s The Electrochemical Society.
Subjects: Electrochemistry
Materials Science
Depositing User: Users 27 not found.
Date Deposited: 09 May 2018 11:58
Last Modified: 09 May 2018 11:58

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