Effect of quenching rate and annealing on ESR of Cu2+ and #betta#-induced Cd+ in low alkali borate glasses

A new ESR hyperfine structure (hfs) of Cu2+ was detected in moderately (cooling rate approx.= 3 K/s) and rapidly (103-105 K/s) quenched borate glasses with Na2O content smaller than 5 mol% in addition to the already reported three patterns, spectra I, II and III, for the moderately quenched borate glasses with 5< or approx.[Na2O]< or approx.13, 20< or approx.[Na2O]< or approx.37 and 55< or approx.[Na2O]< or approx.75, respectively. The ESR parameters of this spectrum were much the same as those of II, but a significant difference was observed between thermal stabilities of these spectra. The newly observed spectrum was named spectrum II'. A superposition of spectra II' and Ii was seen in low alkali borate glasses ([Na2O]< or approx.5 mol%). The relative intensity of II' to I increased remarkably with increasing quenching rate of the melts and with decreasing alkali content under the same quenching condition. In addition, spectrum II' was found to relax into I upon thermal annealing of the glasses. Similar changes were observed also in ESR of the #betta#-induced Cd+ with 5s1 electronic configuration. A tentative model to account for the spectral changes was proposed on the basis of the characteristics of B-O bonding. (orig.)