Optical band gaps and spectroscopy properties of Bi m + /Eu n + /Yb 3+ co-doped ( m = 0, 2, 3; and n = 2, 3) zinc calcium silicate glasses.

In this study, the indirect/direct optical band gaps and spectroscopy properties of Bi m + /Eu n + /Yb 3+ co-doped ( m = 0, 2, 3; and n = 2, 3) zinc calcium silicate glasses under different excitation wavelengths were investigated. Zinc calcium silicate glasses with the main compositions of SiO 2 -ZnO-CaF 2 -LaF 3 -TiO 2 were prepared by the conventional melting method. EDS analysis was performed to determine the elemental composition existing in the zinc calcium silicate glasses. Visible (VIS)-, upconversion (UC)-, and near-infrared (NIR)-emission spectra of Bi m + /Eu n + /Yb 3+ co-doped glasses were also investigated. Indirect optical band gaps and direct optical band gaps of Bi m + -, Eu n + - single-doped, and Bi m + -Eu n + co-doped SiO 2 -ZnO-CaF 2 -LaF 3 -TiO 2 -Bi 2 O 3 -EuF 3 -YbF 3 zinc calcium silicate glasses were calculated and analyzed. CIE 1931( x , y ) color coordinates for VIS and UC emission spectra of Bi m + /Eu n + /Yb 3+ co-doped glasses were determined. Besides, the mechanism of VIS-, UC-, NIR-emissions, and energy transfer (ET) processes between Bi m + and Eu n + ions were also proposed and discussed.