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.