Studies on structural characterization and near white light emission through energy transfer between Ce3+ and Tb3+ in barium gallium borosilicate glasses

Glasses of the composition 30BaO-2Ga(2)O(3)-(27.8-x)B2O3-4OSiO(2)-xCe(2)O(3) (0 <= x <= 1.0) were synthesized by conventional melting and quenching process. The samples were characterized by XRD, EDS, TG-DTA, FT-IR and Raman studies. Optical absorption (OA) and photoluminescence (PL) spectral studies were performed. X-ray diffraction patterns of samples have clearly confirmed the amorphous nature of the samples. Differential thermal analysis indicated thermal stability of glasses. Raman and FTIR spectra have exhibited different fundamental vibrational bands of borate and silicate structural units. The absorption spectra exhibited four absorption bands of Tb3+ ions from the ground state F-7(6) in the visible and NIR regions. In addition, a feeble band corresponding to 4f (F-2(J)) -> 5d ((2)A(1)g) absorption transition of Ce3+ ions at 416 nm is also located in these spectra. Optical bandgap (E-g) evaluated using Tauc plots, is observed to decrease with increase of Ce2O3 up to 0.6 mol%. Luminescence spectra (recorded at lambda(exc) = 329 nm) of glass co-doped with 0.6 mol% CTb exhibited the maximal PL output. The non-exponential time decay profiles are finely fitted to Inokuti-Hirayama (I-H) model for S = 6. This observation suggests that the energy transfer mechanism between Ce3+ -> Tb3+ is connected with the dipole-dipole interaction. The CIE coordinates of 0.6CTb glass are estimated to be (0.257, 0.307). These values are found to be nearer to the standard values of ideal white light and hence it is concluded that the glass of this composition is useful for white LEDs. (C) 2019 Elsevier B.V. All rights reserved.