Glasses of composition [16RO–3Al2O3–6CuO–20Na2O–55P2O5], where R is the alkaline earth (R ¼ Mg, Ca, Sr
and Ba mol. %), were prepared by conventional melt quenching technique. The glass samples were characterized
by X-ray diffraction, infrared spectroscopy, and spectrophotometer. XRD patterns show no sharp peaks indicating
the non-crystalline nature of the prepared glasses. The density and molar volume of the glass systems were
determined in order to study their structures. These results revealed that addition of alkaline earth elements leads
to the formation of non-bridging oxygens (NBOs) and expands (opens up) the structure. The infrared spectra were
analyzed to quantify the present phosphate groups. The optical absorption spectra of Cu2þ ions show the characteristic broadband single of Cu2þ ions in octahedral symmetry. The band gap was estimated following two
methodologies. The first method considers the band edge of the transmission, while the second approach relays on
the estimated values of the optical constants. A decent agreement for the band gap values using the two methods
was obtained