EPR AND MAGNETIC-SUSCEPTIBILITY STUDIES OF CU2+ IONS IN BI2O3.GEO2 GLASSES

Results of EPR and magnetic susceptibility measurements performed on x CuO .(1-x) [Bi2O3 . GeO2] glasses with 0<x less than or equal to 50 mo l% are reported. EPR data suggest a hexacoordinated geometry of the te tragonal-distored octahedral symmetry for Cu2+ ions. The modification of EPR spectra with the increasing of CuO content are explained suppos ing that these are the results of a superposition of two EPR absorptio ns: 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 v s CuO content shows that between clustered copper ions the dipole-dipo le interactions prevail. These data consist with those obtained from m agnetic measurements, which indicate that the Cu2+ ions are magnetical ly 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 glas ses. Copyright (C) 1996 Elsevier Science Ltd