X-ray photoelectron spectroscopic studies of vanadium-strontium-borate [(V₂O₅)_x(SrO)_0.2(B₂O ₃)_0.8-x] oxide glasses

Vanadium-strontium-borate glasses with the chemical composition [(V ₂O₅)_x(SrO)_0.2(B₂O ₃)_0.8-x], where 0.4 ≤ x ≤ 0.8, have been investigated by X-ray photoelectron spectroscopy (XPS). The core-level binding energies of V 2p, Sr 3p, B 1s and O 1s have been measured. The doublet peaks attributed to Sr 3p_3/2 and Sr 3p_1/2 in the Sr 3p spectra have essentially the same binding energies for all glass samples, regardless of the composition, but shifted by about 0.6eV towards higher binding energies than those of the SrO powder. The B 1s peaks, with essentially the same full-width at half-maximum (FWHM), have the same binding energy, which is lower than those of the B₂O₃ powder by ∼0.7 eV. The O 1s core level spectra exhibit significant composition-dependent changes and were deconvoluted into two peaks. The variation in the ratio of the peak areas is discussed in terms of the local structure. The quantitative ratio (V ⁴⁺/V_total), for each glass sample, has been determined from the analysis of the V 2p core level spectra. The ratio remains practically constant independent of vanadium concentration within experimental uncertainties.