ESR OF VANADYL IONS IN LI2O.BAO.B2O3 GLASSES

Glasses with composition x Li2O.yBaO.(100-x-y)B2O3 have been prepared over the range 0 less-than-or-equal-to x less-than-or-equal-to 35 and 0 less-than-or-equal-to y less-than-or-equal-to 35. The electron spin resonance spectra of VO2 + of these glasses have been measured at X-ba nd (nu almost-equal-to 9.12 GHz) at room temperature (RT congruent-to 295 K). Spin Hamiltonian parameters g(parallel-to), g(perpendicular-to ), A(parallel-to), A(perpendicular-to), dipolar hyperfine coupling par ameter, P, and Fermi contact interaction parameters, K, have been calc ulated. It is found that with a decrease in the B2O3 content from 85 m ol% to 65 mol%, the value of g parallel-to, g perpendicular-to, A para llel-to, A perpendicular-to, P and K change from 1.936 to 1.940, 1.980 to 1.976, 172.2 to 166.6, 64.7 to 60.9, 117.4 to 116.1 and 0.819 to 0 .789, respectively, showing that there is an improvement in the octahe dral symmetry of the V4+ site. On the other hand, variations in the Li 2O:BaO ratio for constant B2O3 have no effect on the vanadium site. Th eoretical optical basicity, LAMBDA(th), of the glasses has also been c alculated and is in the range 0.45-0.53.