Structural information in the optical spectra of Eu3+ doped glasses from the ternary system Na2O-B2O3-SiO2

A series of melt derived sodium borate, sodium silicate and sodium borosilicate glasses (with low silica content) doped with 1 mol% Eu2O3 were investigated by means of absorption, luminescence and excitation spectroscopy The structural changes of the host glasses induced by the addition of the modifier give rise to variations of position, width, crystal field splitting and intensity of selected electronic f-f transitions of Eu3+. Additional information on the structural groups in the neighbourhood of the rare earth ions is contained in the vibronic sidebands of the pure electronic transitions. The observed compositional variations in the spectra of the three glass types are interpreted in terms of the oxygen polarisability, Eu-O covalency crystal field strength and Eu3+ site symmetry The results are compared with the Bray model for the ternary glasses.