Lamartine Meda

Investigation of electrochromic properties of nanocrystalline tungsten oxide thin film

Thin films of tungsten oxide were grown by organometallic chemical vapor deposition (OMCVD) using tetra(allyl)tungsten, W(η3-C3H5)4. X-Ray diffraction (XRD) analyses showed amorphous films at substrate temperatures (Ts) 350°C. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed grain sizes in the range 20–40 nm. In situ electrochemical reduction of WO3.2/ITO (2.0 M HCl) produced a faint blue color in less than 1 s. The maximum coloration efficiency (CE) was found to be 22 cm2/mC at 630 nm. The density of the films decreases from 4.53 to 4.29 g/cm3 after annealing. An optical bandgap (Eg) of ∼3.2 eV was estimated for both as-deposited and annealed films.

Chemical Vapor Deposition of Tungsten Oxide

Crystalline and amorphous thin films of tungsten(VI) oxide can be prepared by chemical vapor deposition using a variety of volatile precursors below 500 °C. Deposition parameters for preparation of WO3 films from tungsten hexacarbonyl [W(CO)6], tungsten hexafluoride (WF6), tungsten ethoxides [W(OEt)x, x = 5, 6] and tetra(allyl)tungsten [W(η3-C3H5)4] are summarized. The electrochromic behavior of these films is comparable with that observed for WO3 films prepared by evaporation, sputtering and electrodeposition.

On the Mixed Valence Behavior and Cooperative 3D Ordering of a Series of Tris-Oxalato Ferrates: Bu4N{M FeIII(ox)3}(M═MnII(A),FeII(B), CoII(C), NiII(D) and φ4P{FeIIFeIII(ox)3}(E): New Ferrimagnets

Abstract A combination of a.c. susceptometry and Fe57 Mossbauer spectroscopy measurements confirm valence trapped 3D-ferrimagnetically ordered ground states for the title compounds save (A) that orders antiferromagnetically with a very broad maximum in X′m centered at - 50K. Their ground state magnetic behavior is contrasted with the previously demonstrated ferromagnetism of Bu4N{FeIICrIII(ox3} and φ4P{MnIICrIII(ox3)}.

Electrochemical Properties of Tungsten Oxide Nanowires Compared to Bulk Particles

The electrochemical properties of oxygen-deficient tungsten oxide (W18O49) nanowires were investigated. The nanowires were prepared via a simple thermal evaporation method. The as-deposited nanowires were 60–90 nm in diameter and several micrometers long as measured by field-emission scanning electron microscopy. The crystal structure was indexed to the monoclinic W18O49 phase. The electrochemical properties of the nanowires and WO3 bulk particles were examined by cyclic voltammetry between 2 and 4 V vs Li/Li+. We found that the nanowires cycle better than the bulk particles.