Effect of lead fluoride incorporation on the structure and luminescence properties of tungsten sodium phosphate glasses

Tungsten phosphate glasses are known to be promising materials for several applications in optics such as non linear optical properties, lower phonon energy or photochromic effects related with tungsten oxide incorporation inside the phosphate network. In this study, lead fluoride has been incorporated in a 60NaPO(3)-40WO(3) glass composition according to the ternary molar compositions (100 - x) [0.6NaPO(3)-0.4WO(3)]-xPbF(2) with x varying from 0 to 60 mol%. The structural changes as a function of composition were investigated by thermal analysis, UV-visible absorption, Raman spectroscopy, X-ray diffraction of the crystallized samples, and Eu3+ emission in the visible. While DSC analyzes points out a strong decrease in the glass network connectivity and higher crystallization tendency with increasing PbF2 contents, Raman spectra clearly identify a progressive incorporation of PbF2 in the phosphate network with the formation of terminal P-F and W-F bonds. These results are also in agreement with the crystallization of beta-PbF2 observed for the most lead fluoride concentrated samples. Investigation of Eu3+ emission data in the visible showed longer D-3(0) excited state lifetime values and higher quantum efficiencies. These results are discussed in terms of the assumption of higher local symmetry around Eu3+ with increasing PbF2 contents. (C) 2015 Elsevier B.V. All rights reserved.