Stoichiometry and valence measurements of niobium oxides using electron energy-loss spectroscopy

Qualitative and quantitative electron energy-loss spectroscopy analyses have been performed on niobium and stable niobium oxides (NbO, NbO₂ and Nb₂O₅). At integration windows (Δ) greater than 75 eV, k-factor analysis can be used to distinguish between the stoichiometry of the three oxides within 5.7% error. As seen in other metal oxides, with increasing oxidation state the metal ionization edges shift to higher energies relative to the O-K edge. Normalized M_2,3 white-line intensities show a strong correlation with 4d occupancy for each compound. The data are in correspondence with that observed in the literature for 4d transition metals using normalized L_2,3 white lines. Lastly, a distinctive energy-loss near-edge, structure of the O-K edge was observed for each oxide, which could be used as a fingerprint for analysis of unknowns.