Abstract: Infrared absorption spectra of xCaO(1− x − z)SiO2 zP2O5 glass system with a CaO:SiO2 molar ratio 3:2 and with 0.0⩽ z ⩽0.5 are examined in the region 4000–400cm−1, together with XRD. Deconvoluted spectra were analyzed to determine the position and relative amounts of the IR bands responsible for the different silicate and phosphate units. Bonding mechanism such as Si–O–Si, Si–O–Ca, P–O–P, O–P–O, P13;O− etc. is suggested for random arrangement. A variation in the band positions and the relative amounts of various bonds with P2O5 is also shown. The result indicates that P5+ occupies the network position and forms the linkage Si–O–P in the glass for higher amount of P2O5. This Si–O–P bond may lead to the formation of five and six coordinated silicon in the glass matrix. The bands related to bending mode of H2O molecules and the stretching mode of P–O–H groups forming hydrogen bonding are shown to result in several bands in the 1521–1700 and 1758–3059cm−1 range, respectively. X-ray diffraction pattern of the base samples, within the detection limit, shows that all are homogeneous glasses and on optical inspection they did not show any evidence of phase separation. [Copyright &y& Elsevier]