EPR and magnetic susceptibility studies of vanadium lead-borate glasses

EPR and magnetic susceptibility experiments have been performed on x(V₂O₅) (1−x) [2B₂O₃ · PbO] glasses with x varying in the range 0.2 ⩽ x ⩽ 55 mol %. The modifications of the EPR spectra with the increasing of V₂O₅ content are explained supposing that these are the result of the superposition of two EPR signals, one with a well resolved hyperfine structure typical for isolated vanadyl ions and one consisting from a broad line without structure typical for clustered ions. The last species of ions is dominating in the glasses with x > 45 mol % V₂O₅.

For the samples with x ⩾ 35 mol % V₂O₅ the reciprocal magnetic susceptibility follows the Curie behaviour. From magnetic data and considering that only V⁴⁺ and V⁵⁺ ions occur in the studied glasses we have estimated the V⁴⁺ ions content as well as the N_V⁴⁺/N_V⁵⁺ ratio, the last being approximately constant⁺ ∼ 0.14.