EPR and magnetic susceptibility studies of Cu2+ ions in Bi2O3.GeO2 glasses

Results of EPR and magnetic susceptibility measurements performed on xCuO .(1-x) [Bi2O3 . GeO2] glasses with 0<x less than or equal to 50 mol% are reported. EPR data suggest a hexacoordinated geometry of the tetragonal-distored octahedral symmetry for Cu2+ ions. The modification of EPR spectra with the increasing of CuO content are explained supposing that these are the results of a superposition of two EPR absorptions: one is asymmetrical, typical for isolated Cu2+ ions (g(parallel to) congruent to 2.34 and g(perpendicular to) congruent to 2.07) and the another a symmetrical line at g congruent to 2.10, characteristic for clustered ions. The dependence of the g congruent to 2.10 linewidth vs CuO content shows that between clustered copper ions the dipole-dipole interactions prevail. These data consist with those obtained from magnetic measurements, which indicate that the Cu2+ ions are magnetically isolated. From the Curie constants it was established that in this glass system the copper ions are in both Cu+ and Cu2+ valence states, the latter being approximate to 45% of CuO content in all studied glasses. Copyright (C) 1996 Elsevier Science Ltd