The FTIR study reveals the presence of BO3, BO4 vibration groups and the bending of B–O–B units. The asymmetric stretching of BO3 and BO4 was apparent at higher Dy2O3 concentrations. More tetrahedral BO4 units were formed by increasing Dy2O3 concentrations. The dependency of Dy2O3 concentrations on the optical properties is further discussed with other important physical properties.