EUROPIUM SITE SELECTIVE SPECTROSCOPY OF ALUMINOBOROSILICATE GLASSES - STRUCTURAL APPROACH AND INFLUENCE OF PHOSPHORUS ON THE ENVIRONMENT OF THE LANTHANIDE

The spectroscopic properties of europium Eu3+ have been applied to the structural investigation of AlB-silicate glasses. For two samples in which has been added 1 and 2 mol% P2O5, it is concluded that an oxyapatite-type environment is formed for some of the europium ions. A crystallized apatite phase has been identified by X-ray diffraction in the opalescent core of the most heavily doped sample (2% P2O5) but not in its transparent part, and not in the other sample (1% P2O5). The spectroscopic data observed for the samples with P2O5 {reversed tilde equals} 0.1% show that the distribution of environments around Eu3+ is very similar for these glasses and all the oxide glasses previously investigated. The crystal field strength, reduced to rank k = 2 parameters, Bqk, expressed by B2 = [(B)in022 + 2(B22)2] 1 2 varies from 485 to 1920 cm-1 in a monotonic way with respect to the 5D0→ 7F0 energy, which ranges from 17220 to 17490 cm-1 with no marked change within the site distribution. Site to site energy transfer is observed at 300 K by time resolved selective excitation of a small subset of ions. The effective transfer rate deduced from different approximations is 350 ± 250 s-1. The minimum Eu-Eu distance may be estimated to about 0.5 nm, whereas the average distance deduced for an homogeneous distribution is 1.6 nm. © 1990.