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Investigated compositions were prepared from the starting compounds NH 4 H 2 PO 4 48% in P 2 O 5 , Na 2 CO 3 98%,WO 3 99,9%, PbF 2 99,9%, Er 2 O 3 99,99% and Yb 2 O 3 99,99%, all from Aldrich. The starting powders were weighted using an

a b s t r a c tTungsten 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 À 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 Eu 3+ emission in the visible. While DSC analyzes points out a strong decrease in the glass network connectivity and higher crystallization tendency with increasing PbF 2 contents, Raman spectra clearly identify a progressive incorporation of PbF 2 in the phosphate network with the formation of terminal PAF and WAF bonds. These results are also in agreement with the crystallization of b-PbF 2 observed for the most lead fluoride concentrated samples. Investigation of Eu 3+ emission data in the visible showed longer 5 D 0 excited state lifetime values and higher quantum efficiencies. These results are discussed in terms of the assumption of higher local symmetry around Eu 3+ with increasing PbF 2 contents.

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