Sol-gel synthesis and XPS characterization of sodium-vanadium oxide bronze thin films

A sodium-vanadium oxide bronze has been synthesized by using a sol-gel technology from V2O5 and Na2SO4. The powders were dissolved in hydrogen peroxide solution and heated up to 350 K for the dissociation of the peroxide complexes. The obtained gel was deposited on a metallic substrate and dried in air at room temperature. The produced xerogel was heated up to 580 K in pure oxygen atmosphere for the removal of water from the xerogel. Starting materials, xerogel, as well as a final product were investigated by means of XPS method. The binding energies of the V 2p peaks were shifted by 0.4 eV to the smaller BE values in comparison with the pure vanadium pentoxide powder and xerogel. Na 1s BE in the bronze is larger than in the Na2SO4 powder and xerogel by 0.7 and 0.8 eV, respectively. XPS spectra testify that the chemical bonds of vanadium, oxygen and sodium in the bronze differ from similar bonds in the starting materials. The sulphur presence was detected only in the xerogel but not in the final bronze composition