Structure and magnetic properties of vanadium–sodium silicate glasses

Vanadium–sodium silicate glasses with the chemical composition [(V2O5)x(Na2O)0.30(SiO2)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 2p3/2 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.