Characterization of oxides on niobium by raman and infrared spectroscopy

摘要

The combination of electrochemical methods, laser Raman spectroscopy (LRS), surface-enhanced Raman scattering (SERS) and infrared reflection absorption spectroscopy (IRRAS) have been used to demonstrate that a stable passivated film can easily beformed on Nb in 0.15 M NaCl. The composition of the film has been identified to be NbO{sub}2 and different forms of Nb{sub}2O{sub}5. From LRS, the film formed in 0.10 M NaOH has similar composition. A longer exposure of the Nb electrode to air favors theconversion of NbO{sub}2 to the more stable Nb{sub}2O{sub}5 and the transformation of B-Nb{sub}2O{sub}5 to H-Nb{sub}2O{sub}5. In situ analysis of the passivated film in 0.15 M NaCl was carried out by coupling the electrochemical technique with LRS andSERS. The results indicated the presence of different forms of Nb{sub}2O{sub}5 at the metal/solution interfaces.