The structures of xCuO · (1 − x)P2O5 glasses (0 less-than-or-equals, slant x less-than-or-equals, slant 0.50) prepared in vacuum sealed silica ampoules were investigated using vibrational spectroscopies. with the addition of CuO, both infrared and Raman spectra indicate a systematic transformation from a three-dimensional ultraphosphate network dominated by Q3 tetrahedra into a chain-like metaphosphate structure dominated by Q2 tetrahedra. IR spectra clearly show two distinct Q3 sites with bands at 1378 and 1306 cm−1, assigned to Pdouble bond; length as m-dashO bonds on isolated Q3 tetrahedra and Pdouble bond; length as m-dashO bonds on View the MathML source tetrahedra that participate in the coordination environments of the Cu-octahedra, respectively. As CuO content increases, the intensity of the Pdouble bond; length as m-dashO band associated with the View the MathML source tetrahedra increases to a maximum x not, vert, similar 0.33, then decreases with a concomitant increase of the intensity of the band at 1265 cm−1, due to the asymmetric vibration of the PO2 groups on Q2 tetrahedra. when x > 0.33 the isolated Cu-octahedra begin to share common oxygens to form a sub-network in the phosphate matrix. The effects of glass structure on the glass properties, including density, refractive index, and glass transition temperature, are discussed.