Sol-gel chemistry of transition metal oxides

Physics of Amorphous Silicon–Carbon Alloys

Crystalline VO2.5 films were prepared by reactive dc magnetron sputtering followed by annealing posttreatment. Lithium was inserted electrochemically from an electrolyte so that LixVO2.5 (0<x<1.5) was formed. The evolution of the electromotive force (EMF) was recorded during Li intercalation. For lithiated samples, structure by x‐ray diffraction, optical properties by spectrophotometry in the 0.3–2.5 μm range, infrared reflectance by spectrophotometry in the 400–1200 cm−1 interval, and the mechanical stress by beam deflectometry were studied. Changes in lattice parameters, phonon spectra, and stress levels gave a consistent picture of the structural evolution. Measurements of optical absorption and EMF were interpreted within a conceptual model of interband transitions between the O 2p band and a split V 3d band. Durability and reversibility of the Li intercalation/deintercalation were verified by potentiodynamic measurements. For comparison, the properties of highly disordered films were also measured.

Electrochromic Vanadium-pentoxide- based Films: Structural, Electrochemical and Optical Properties

A wide range of vanadium oxides have been obtained via the hydrothermal treatment of aqueous V(V) solutions. They exhibit a large variety of nanostructures ranging from molecular clusters to 1D and 2D layered compounds. Nanotubes are obtained via a self-rolling process while amazing morphologies such as nano-spheres, nano-flowers and even nano-urchins are formed via the self-assembling of nano-particles. This paper provides some correlation between the molecular structure of precursors in the solution and the nanostructure of the solid phases obtained by hydrothermal treatment.

https://www.mdpi.com/1996-1944/3/8/4175/pdf

Hydrothermal Synthesis of Nanostructured Vanadium Oxides

Bilayered Nanostructured V2O5·nH2O for Metal Batteries

Mixed-valence vanadium pentoxide gels have been obtained by polymerization of vanadic acid. They exhibit semiconducting properties which arise from electron hopping between VIV and Vv ions. Such gels can easily be deposited onto a substrate, giving layers of high electrical conductivity (σ =0.l Ω−1 cm−1 at 300 K). Their electrical properties can be described by the small-polaron model, and the main parameters have been determined by conductivity measurements, E.S.B. and optical spectroscopy. The optical and thermal activation energies are found to be E opt = 0.87 eV and Eth = 0.17eV. The transfer integral J = 0 05 eV is quite small, and the electron–phonon coupling parameter γ = 14 is rather high. The structural disorder of this amorphous semiconductor was estimated from electrical and E.S.R. experiments. It leads to a localization of the charge carriers.

Semiconducting properties of V2O5 gels

Measurements are reported on the optical gap, dark conductivity and photoconductivity of hydrogenated amorphous silicon-carbon films (a-SiC : H) prepared from the glow-discharge decomposition of si...

J. Bullot

Papers

Semiconducting properties of V2O5 gels

Electronic and optical properties of glow-discharge amorphous silicon-carbon alloys