The local structure and interactions between V4+ ions in soda-phosphate glasses

EPR investigation on xV(2)O(5).(100 - x)[2P(2)O(5). Na2O] and xV(2)O(5).(10 0 - x)[P2O5. mNa(2)O] (m = 1.5 and 2) glass systems was performed. The chan ges observed in the EPR spectra of xV(2)O(5)X (100 - x)[2P(2)O(5). Na2O] gl asses with increasing content of vanadium oxide are explained supposing tha t these spectra consist of two superposed EPR signals, one with hyperfine s tructure typical for isolated ions and another one consisting of a broad li ne without hyperfine structure characteristic for clustered ions. The clust ered V4+ ions are not evidenced at low V2O5 contents (x = 5 mol%). The EPR spectra of xV(2)O(5).(100 - x)[P2O5. mNa(2)O] glasses indicate a superposit ion of two or three hyperfine structures attributed to nonequivalent VO2+ c enters. Spin Hamiltonian parameters (g, A), dipolar hyperfine coupling para meter (P) and Fermi contact interaction term (K) have been evaluated. The r atio between the number of clustered and isolated ions was also determined.