IR and EPR studies on some lithium-borate glasses with vanadium ions

The IR spectra of the xV(2)O(5)(100 - x)[2B(2)O(3). Li2O] glasses contain the bands characteristic for B2O3(delta (B-O-B) = 700 cm(-1), (v) over bar (B-O) = 1250 cm(-1)). Li2O ((v) over bar (Li-O) = 415 cm(-1)) and V2O5((v) over bar (V-O) = 950 cm(-1)) groups. EPR spectra for the glasses with small contents of V2O5 (x > 5 mol%) show a well-resolved hyperfine structure typical for isolated vanadyl ions in a ligand field of near octahedral (O-h) symmetry. For x > 20 mol% the EPR spectra may be considered as a superposition of two signals: one with the resolved hyperfine structure for isolated VO2+ ions in a C-4v, symmetry and another broad line without structure at g approximate to 1.96 for associated vanadium ions. The clustered ions are due to the dipole-dipole interactions between V4+ ions and their number increases with the V2O5 content. The spectroscopic studies indicate that the V2O5 oxide becomes a former of the network at high concentration (x > 20 mol%) together with B2O3 (C) 2001 Elsevier Science B.V. All rights reserved.