Niobium oxide films are promising cathodic electrochromics that in many aspects can compete with the more frequently studied WO$_3$ films. The films reported herein were prepared using the sol-gel route from a NbCl$_5$ precursor. The electrochromic properties were pronounced for crystalline films that are heat-treated at 500^oC and exhibited transmittance changes between coloured and bleached states of 60 \% in the UV and 80 \% in the VIS-NIR regions. Improved bleaching and more reversible electrochromism of thick niobium oxide films (d $>$ 250 nm) were obtained by lithiation.
MAÇEK, M. and OREL, B. (1998) "Electrochromism of Sol-gel Derived Niobium Oxide Films," Turkish Journal of Chemistry: Vol. 22: No. 1, Article 8. Available at: https://journals.tubitak.gov.tr/chem/vol22/iss1/8