Growth of nanotubes in sol-gel-derived V₂O₅ powders and films prepared under acidic conditions

Abstract

The structural evolution with temperature of some V2O5 gels and thin films is presented, and the role of the hydrolysis conditions is investigated. Several techniques, i.e., x-ray diffraction, differential thermal analysis, infrared, and temperature-dependent Raman spectroscopy, have been used to follow the thermal behavior of the samples. When the bulk xerogels begin to change from a nanocrystalline phase to the orthorhombic α-V2O5, in the temperature range 280 to 300 °C, a growth of vanadium oxide nanotubes also occurs, while at higher temperatures the crystallization into the α phase prevails. A slightly different evolution is observed for heat treated thin films, which show a structure containing polyvanadate chains near room temperature. They also present a growth of nanotubes for intermediate temperatures and a complete crystallization into the α phase when the temperature is further increased.

Improved Electrochromic Properties of Vanadium Pentoxide Nanorods Prepared by Thermal Treatment of Sol-Gel Dip-Coated Thin Films

“…The characteristic bands of V 2 O 5 appear in the spectrum of samples treated at 300 • C and become more prominent for the samples annealed at 500 • C. In the high-frequency region, the strong band at 1006 cm −1 corresponds to the V=O stretching vibration of the vanadyl unshared oxygen, [36][37] coincide with the beginning of the formation of the nanostructures. 39 Our Raman results on the crystallization are in agreement with XRD data on the sol-gel films. [40][41] Effect of heat-treatment on the electrochromic properties of vanadium pentoxide thin films.-The electrochromic properties of the films were studied as a function of their thickness and annealing temperature.…”

Electrochromic thin films of sodium intercalated vanadium(V) oxide xerogels: Chemical bath deposition and characterization

“…However, there is a great similarity with the patterns of V 2 O 5 ·nH 2 O xerogel (PDF 40-1296) with the difference that our patterns exhibit additional peaks. From the literature survey on vanadium oxides [6,[26][27][28][29] it is well known that the X-ray patterns of V 2 O 5 ·nH 2 O xerogel are characterized by a small number of 3-5 broad peaks from the series of 00l reflections (missing 002 peak). Moreover, the intensity of the first order diffraction 001 located generally around d = 11.5 Å is much larger than that of the other terms.…”

Influence of vanadium concentration and temperature on the preparation of electrochromic thin films of ammonium intercalated vanadium(v) oxide xerogel nanoribbons

“…26 This determines the typical XRD pattern of the xerogels that is characterized by a small number of 3-5 broad peaks from the series of 00l reflections (missing 002 peak) with a pronounced 001 peak located generally around 11.5 Å. 5,13,28 It was reported that the intercalation of cations like Na + and TMA + (tetramethyl ammonium) into the xerogel leads to the appearance of extra diffraction peaks in the diffraction patterns of M 0.3 V 2 O 5 •1.5H 2 O. 25 Durupthy et al 25 have suggested that the observation of hkl set of reflections (instead of 00l only) is related to the loss of ordered stacking of the double V 2 O 5 layers.…”

“…10,11 Most recently, Costa et al reported that the electrochromic cell based on an inkjet printed vanadium oxide xerogel on flexible PET/ITO electrode exhibits excellent colour contrast between different redox states and excellent cycling stability (more than 30 000 cycles with a degradation of 18%) which characteristics make it very promising for application in intelligent windows. 2 Vanadium(V) oxide xerogels (solids and thin films) are most often prepared by sol-gel method in three main variants (using three synthetic routes): acidification of metavanadate aqueous solutions, 5,10,12 hydrolysis condensation of alkoxides 5,7,13,14 and reaction between H 2 O 2 and V 2 O 5 powder. 2,15 a Other methods such as hydrothermal, 16 sputtering, 17,18 electrodeposition, 19 laser ablation techniques, 20 inkjet printing, 2 etc.…”