Caracterization of Nb2O5 thin films with electrochromic properties

The sols for thin electrochromic coatings of Nb2O5 were obtained by synthesis of the niobium butoxide from BuONa and NbCl5. The similar to 300nm thick films were deposited by dip-coating technique from the alkoxide solution and calcined at 560 degrees C in O-2 atmosphere during 3 hours. The particles size of niobium oxide (V) powder (similar to 20 mu m) was obtained from x-ray diffraction using the Scherrer equation. The coatings mere characterized by cyclic voltammetry and cronoamperommetry techniques. The spectral variation of the optical transmittance were determined in situ as a function of the cyclical potencial and memory effect. The insertion process of lithium is reversible and change the film color from transparent (T=80%) to dark blue (T=20%).