Structural analysis and luminescence studies of Ce3+: Dy3+ co-doped calcium zinc gadolinium borate glasses using EXAFS

Abstract

Ce3+: Dy3+- codoped calcium zinc gadolinium borate glasses were synthesized by traditional melt quenching technique. These glasses after synthesizing they were characterized through density, molar volume, refractive index, FTIR, absorption spectra, photoluminescence properties, structural studies using XANES/EXAFS and life time profile analysis. XANES spectra of Gd LIII-edge and Dy LIII-edge for 20CaCO3 - 20 ZnO - 10Gd2O3 - 49.5B2O3 - 0.5Dy2O3 (C2) and 20CaCO3 - 20 ZnO - 10Gd2O3 – 49B2O3 - 0.5Dy2O3 - 0.5CeF3 (D) glass showed absorption edge at 7249.8 eV and 7795.7 eV respectively confirming the presence of Gd3+ and Dy3+ ions. Ce-LIII edge for D glass shows peaks at ~ 5728 eV confirming the presence of Ce3+. The Judd-Ofelt (JO) theory investigations have been applied for Dy3+ ions to calculate the Judd-Ofelt (JO) intensity parameters and found that the trend follows Ω2> Ω4> Ω6. The ionic nature of RE3+-O were evaluated by using bonding parameter (δ) value for C2 and D glass and found to be −0.0076 and −0.0102. Radiative properties were subsequently estimated using JO parameters and investigated radiative transition probabilities (AR), stimulated emission cross section (σR) and branching ratio (βR). The photoluminescence and radio luminescence spectra exhibit two prominent emission peaks at 484 (blue) and 575 nm (yellow) that corresponds to the4F9/2 → 6H15/2 and4F9/2 → 6H13/2 transitions respectively. The chromaticity coordinates were evaluated and found that these coordinates positioned in the white region with (x, y) = (0.348 0.382) and (0.325, 0.353) values for C2 and D glasses. The fluorescence decay from the 4F9/2 level was measure by monitoring the intense 4F9/2 to 6H9/2 transition. The decay time is found to be bi-exponential when monitored at λexi = 387 nm. The results obtained in present work demonstrate that the present glasses could be potential candidate for use in white light solid state lighting applications.