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The structural and spectroscopic properties of Na 2 O-Al 2 O 3 -SiO 2 -xP 2 O 5 glasses (x = 0 to 7 mol%) are investigated. Both Raman and IR spectra reveal that discrete phosphate species ([PO 4 ] −3 , [PO 3 O 1/2 ] −2 ) with low polymerization degree can be formed in the silicate glass. These phosphate structures scavenge non-bridging oxygen ions and cations from the silicate network, resulting in an increase of the glass transition temperature. According to the Judd-Ofelt intensity parameters (Ω2,Ω4,Ω6) of Er 3+ , the asymmetry of local environment around Er 3+ becomes higher, and the bond covalency between Er 3+ and O 2− decreases after P2O5 is introduced. In the emission spectra, photoluminescence intensity increases with increasing P2O5 concentration and the spectra are inhomogeneously broadened, revealing that the ligand electric field around Er 3+ is dramatically changed, and the glass matrix becomes disordered. OCIS codes: 160.2750, 160.5960. doi: 10.3788/COL201210.071602. Recently, phosphosilicate glass has gained considerable attention due to its applications in multiwavelength fiber laser and rare earth (RE) ion-doped optical glass fibers [1−4] . The addition of P 2 O 5 improves the quantum efficiency of RE radioactive transitions [5−7] , and the addition of phosphate also highly limits photo-darkening due to the formation of color centers [8,9] . In phosphosilicate glass research, the solubility of P 2 O 5 in the silicate matrix is an inevitable problem [10] ; moreover, the existence species of phosphate and their interaction with silicate network can greatly influence the structural and spectroscopic properties of the glass. To our knowledge, previous studies focus only on the phosphorous speciation changes in phosphosilicate glasses [11,12] . Few reports mention the host environment around the doped RE ions, the effect of phosphate addition on the emission spectrum, or the inner correlation between spectroscopic properties and the local structure.In this letter, various amounts of P 2 O 5 are introduced into the sodium aluminosilicate glass. The structural evolution induced by the addition of P 2 O 5 is investigated based on Raman and infrared (IR) absorption spectra. Er 3+ ions are added into the glass to investigate the environment of RE ions in our phosphosilicate glasses. With the absorption and emission spectroscopic analysis, the relationship between the glass structure and the spectroscopic properties is discussed.A series of sodium aluminosilicate glass samples with the composition of 30Na 2 O-5Al 2 O 3 -(65-x)SiO 2 -xP 2 O 5 -yEr 2 O 3 (x =0, 1, 3, 5, and 7 mol%, y=0 and 0.75 mol%) were prepared by melt-quenching method. Analytical reagent grade powders of Na 2 CO 3 , Al(OH) 3 , Al(PO 3 ) 3 , SiO 2 , and 99.99% high purity powders of Er 2 O 3 were used as raw materials. Then, 50 g of well-mixed powders were melted in platinum crucible for 60 min in the temperature of 1 450• C. The melt was quenched on a preheated steel plate and then annealed for 3 h at the temperature of 560 • C. ...