EPR Spectroscopy of the Mn~(2+) and Cu~(2+) Centres in Lithium and Potassium-Lithium Tetraborate Glasses

摘要

The electron paramagnetic resonance spectra of the glasses with Li_2B_4O_7 and KLiB_4O_7 compositions doped with Mn and Cu were investigated. On the basis of obtained EPR spectra analysis it was shown that the Mn and Cu impurities are incorporated into the glass network as Mn~(2+) (~6S_(5/2), 3d~5) and Cu~(2+ )(~2D_(5/2), 3d~9) ions. The Mn~(2+) EPR spectra in the glasses with Li_2B_4O_7 and KLiB_4O_7 compositions are characterised by the following parameters, measured at T = 300 K: isotropic g-factor (g_(iso) = 2.00 ± 0.05), isotropic hyperfine constant (A_(iso) = (8.65 ± 0.05) mT) and peak-to-peak linewidth of hyperfine components ΔB_(PP) = (3.50 ± 0.05) mT. The Cu~(2+) EPR spectra in the glasses with Li_2B_4O_7 and KLiB_4O_7 compositions, registered at T = 300 K are characterised by the same g-values (g‖ = 2.34 ± 0.05, g┻ = 2.06 ± 0.05) and peak-to-peak line width of hyperfinerncomponents (ΔB~‖pp = (5.11 ± 0.05) mT, ΔBp~±Pp = (1.80 ± 0.05) mT), whereas anisotropic hyperfine constants show some differences (A‖ = (14.28 ± 0.05) mT, A_┻ = (2.34 ± 0.05) mT for glass with Li_2B_4O_7 composition and A|| = (14.21 ±0.05) mT, A_┻ = (2.55±0.05) mT for glass with KLiB_4O_7 composition). The possible local structure of the Mn~(2+) and Cu~(2+) centres in the lithium and potassium-lithium tetraborate glass network has been considered.