EPR studies of Cu2+ and V4+ ions in phosphate glasses

Two lead-phosphate glass systems doped with both copper and vanadium ions i n different ratios were studied by EPR (electron paramagnetic resonance) me thod. EPR spectra and parameters (g(parallel to) = 2.44, g(perpendicular to ) = 2.08 and A(parallel to) = 117.6.10(-4) cm(-1)) obtained for x(CuO . V2O 5)(1-x)[2P(2)O(5). PbO] glasses with x less than or equal to 10 mol% sugges t a tetrahedral (Td) coordination of Cu2+ ions and not a tetragonally elong ated octahedron as has been assumed in previous works. The ground state of the paramagnetic electron is the d(xy) copper orbital with a 4p(x) contribu tion of 6%. For 20 less than or equal to x less than or equal to 40 mol% a broad line (Delta B = 307 G) characteristic for clustered ions appears at g = 2.18. The V4+ ions are evidenced only in the spectra of x(CuO . 2V(2)O(5 ))(1-x)[2P(2)O(5). PbO] glasses and the resonance parameters suggest a pent acoordinated C-4v local symmetry for these ions. The hyperfine structures c haracteristic for Cu2+ and V4+ ions disappear for 10 less than or equal to x less than or equal to 40 mol% due to the mixed exchange Cu2+-V4+ pair for mation in these glasses.