Structure and magnetic properties of vanadium-sodium silicate glasses

Vanadium-sodium silicate glasses with the chemical composition [(V₂O₅)_x(Na₂O)_0.30(SiO ₂)_0.70-x] (0.0≤x≤0.10) have been studied by X-ray photoelectron spectroscopy (XPS) and magnetization measurements. The core-level binding energies of O 1s, V 2p and Si 2p in these glasses have been measured for surfaces produced by in vacuo fracture. The peak position and width of the V 2p_3/2 peak are independent of the V₂O₅ content while the O 1s core-level spectra show significant composition-dependent changes. Two distinct peaks are resolvable arising from the bridging oxygen and non-bridging oxygen (NBO) atoms in the silicate glasses. The fraction of NBO, determined from these spectra is found to increase with increasing V₂O₅ content in the glass and are consistent with the formation of predominantly alkali metavanadate species. The magnetic susceptibility data of these glasses indicate a large, temperature-independent diamagnetic contribution arising from the glass matrix as well as small paramagnetic contribution from the V⁴⁺ ions. The V⁴⁺ content deduced from the magnetization results (∼2%) is below the detection limit of XPS analysis.