Localized Sn²⁺ emission center independent of the optical basicity of zinc phosphate glass

We report the emission and optical properties of RO-substituted (R = Mg, Ca, Sr, and Ba) 2.5SnO-57.5ZnO40P₂O₅ glasses. Although the optical basicity of the host glass is changed by substitution of RO for ZnO, the optical band edge and the peak positions of the photoluminescence (PL) and PL excitation (PLE) spectra show no significant changes. Considering the characteristics of ns²-type emission centers, the properties of which are strongly affected by the coordination field, it can be concluded that the localized Sn²⁺ state affects both the optical absorption edge and the emission.