Grey, brown and blue coloring sol-gel electrochromic devices

Pure and doped niobium oxide (Nb2O5) layers are electrochromic (EC) materials which change their colour by insertion of Li+ ions from transparent to brown, grey or blue depending on the crystallinity of the layer. EC-devices with the configuration K-glass / EC-layer / composite electrolyte / Ion-storage (IS) layer / K-glass, were produced using different Nb2O5 EC-layers, a (CeO2)x(TiO2)1-x (x=0.45) IS-layer and an inorganic-organic composite electrolyte to which a small amount of water (up to 3 wt%) was added. The grey coloring all-solid-state sol-gel devices fabricated with Nb2O5:Mo coatings show a high reversible colouration (DeltaOD = 0.3) and a longterm stability of more than 55000 switching cycles. Large area EC-devices (30 cm x 40 cm) show a transmittance change between 60% and 25% at 550 nm after galvanostatic colouration and bleaching for 3 min and a colouration efficiency of 27 cm²/C. The results obtained with blue and brown colouring Nb2O5 EC-layers and a comparison with blue coloring WO3 layers are also presented

Concerning the structure of hydrogen molybdenum bronze phase III. A combined theoretical-experimental study

10.1021/cm050940oChemistry of Materials17245957-5969CMAT

High performance electrochromic devices based on anodized nanoporous Nb2O5

Despite the predictions, the true potential of Nb2O5 for electrochromic applications has yet to be fully realized. In this work, three-dimensional (3D) compact and well-ordered nanoporous Nb2O5 films are synthesized by the electrochemical anodization of niobium thin films. These films are formed using RF sputtering and then anodized in an electrolyte containing ethylene glycol, ammonium fluoride, and small water content (4%) at 50 °C which resulted in low embedded impurities within the structure. Characterization of the anodized films shows that a highly crystalline orthorhombic phase of Nb2O5 is obtained after annealing at 450 °C. The 3D structure provides a template consisting of a large concentration of active sites for ion intercalation, while also ensuring low scattering directional paths for electrons. These features enhance the coloration efficiency to 47.0 cm2 C?1 (at 550 nm) for a 500 nm thick film upon Li+ ion intercalation. Additionally, the Nb2O5 electrochromic device shows a high bleached state transparency and large optical modulation

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Brockhinke A, Krüger J, Heusing M, Letzgus M. Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames. APPLIED PHYSICS B. 2012;107(3):539-549

Enhanced coloration efficiency for electrochromic devices based on anodized Nb2O5/electrodeposited MoO3 binary systems

There is a continuous quest for developing electrochromic (EC)transition metal oxides (TMOs) with increased coloration efficiency. As emerging TMOs, Nb2O5 films, even those of ordered anodized nanochannels, have failed to produce the required EC performance for practical applications. This is attributed to limitations presented by its relatively wide bandgap and low capacity for accommodating ions. To overcome such issues, MoO3 was electrodeposited onto Nb2O5 nanochannelled films as homogeneously conformal and stratified α-MoO3 coatings of different thickness. The EC performance of the resultant MoO3 coated Nb2O5 binary system was evaluated. The system exhibited a coloration efficiency of 149.0 cm2 C−1, exceeding that of any previous reports on MoO3 and Nb2O5 individually or their compounds. The enhancement was ascribed to a combination of the reduced effective bandgap of the binary system, the increased intercalation probability from the layered α-MoO3 coating, and a high surface-tovolume ratio, while the Nb2O5 nanochannelled templates provided stability and low impurity pathways for charge transfer to occur