Optical properties of sol-gel derived vanadium oxide films

Abstract

Abstract. Vanadium oxide gels can be made from vanadate aqueous solutions or from vanadium alkoxides. The condensation of vanadic acid gives long ribbon-like oxide particles which macroscopically orient in the same direction in aqueous sols when their concentration is larger than 0.12 mol.1-1 . These anisotropic sols and gels should be considered as lyotropic nematic liquid crystals. Thick films in which ribbons align along the same direction can be deposited. These oriented coatings exhibit improved electrochemical properties as reversible cathodes for lithium batteries. Amorphous oxo-polymers are formed via the controlled hydrolysis of vanadium alkoxides. They allow the deposition of optically transparent thin films that exhibit interesting electrochromic properties and turn reversibly from yellow to green upon electrochemical reduction. Moreover these alkoxide derived films can be easily reduced into vanadium dioxide. These VO2 thin films exhibit thermochromic properties and could be used as optical switches in the infrared. The transition temperature of these VO2 films can be modified by doping the vanadium oxide with other cations.

A novel inorganic precipitation–peptization method for VO 2 sol and VO 2 nanoparticles preparation: Synthesis, characterization and mechanism

“…Finally, the green 1 sol was prepared. The color of the prepared sol is consistent with those of other reports [12,13]. The schematic of inorganic precipitationpeptization route for preparation of VO 2 sol is shown in Fig.…”

Electrochromic properties of V2O5−z thin films sputtered onto flexible PET/ITO substrates

“…Vanadium oxide has been prepared by a variety of methods, including evaporation [15,[20][21][22], d.c. sputtering [23], r.f. sputtering [24][25][26], pulsed laser deposition [27], plasmaenhanced chemical vapor deposition [28,29], electrochemical deposition [30][31][32] and sol-gel [33][34][35][36][37][38][39][40][41][42] preparations. However, the electrochromic performance of a-V 2 O 5 − z films deposited on Films were characterized to give insight into the nature of the coatings: the films' surfaces were studied by X-ray photoelectron spectroscopy (XPS) and field emitted scanning electron microscopy (FESEM).…”

XPS and optical properties of sol-gel processed vanadium pentoxide films

“…It should be noted that the fabricated thin films of V 2 O 5 ·nH 2 O were optically isotropic, in contrast to the films of thickness ∼50 µm with n < 400 [21]. It is reasonable to assume that a certain amount of water still persisted in the samples under investigation resulting in the formation of isotropic phase (n > 600 [21]) with anisotropic droplets dispersed within an isotropic gel.…”

“…It is reasonable to assume that a certain amount of water still persisted in the samples under investigation resulting in the formation of isotropic phase (n > 600 [21]) with anisotropic droplets dispersed within an isotropic gel.…”