Silver aggregates in photoluminescent phosphate glasses of the 'Ag2O-ZnO-P2O5' system

Photoluminescent properties of glasses of the Ag2O-ZnO-P2O5 system are reported. The compositions of the glasses are limited by the polyphosphate and diphosphate domain of this system. The phosphate structural units of the network former are deduced from Raman spectra. A comparison with the luminescent properties of crystallized silver phosphates of similar composition allows identification of two different emitting centers: isolated Ag+, Ag+-Ag+ pairs, and a third center resulting from an Ag+-Zn2+ interaction. The introduction of 1 mol% SiO2 or Al2O3 in these glasses leads to precipitation of silver particles, whose dimensions range from nanometers to micrometers, and to the appearance of luminescent centers (Ag-2)(+) detected around the micrometer particles by optical microscopy. We assume that these centers are an intermediate stage during the process of silver precipitation. (C) 1999 Elsevier Science E.V. All rights reserved.