Energy transfer and luminescence study of Dy3+ doped zinc-aluminoborosilicate glasses for white light emission

Abstract

A series of Dy3+ doped aluminoborosilicate glasses with general formula 20SiO2-(40-x) B2O3–10Al2O3–20NaF2–10ZnO-xDy2O3 (x = 0, 0.1, 0.5, 1.0. 1.5, 2.0 and 2.5 mol %) were prepared by melt-quenching method. The FTIR analysis confirms the presence of stretching and bending vibrations of BO4, BO3 and SiO4 units in the prepared glasses. DTA results show that Tg is decreasing with addition of Dy3+ ions in the glass system. Theoretically calculated mechanical properties such as elastic modulus, bulk modulus, shear modulus and Poisson's ratio suggest the increase in mechanical stability of glasses with dysprosium addition. Also experimental analysis carried out using Vicker's microhardness suggests glass stability with applied loads. Absorption spectrum shows twelve bands that exist due to transition from 6H15/2 level to different excited levels. Nephelauxetic ratio and bonding parameter calculated shows decreasing ionicity of glasses with increase in Dy3+ ions. Judd-Oflet parameter calculated for all the glasses follow the trend Ω6 > Ω4 > Ω4. Luminescence study shows three emission peaks having transitions from 4F9/2 → 6H15/2 (blue), 4F9/2 → 6H13/2 (yellow) and 4F9/2 → 6H11/2 (red). Radiative parameters calculated suggest higher stimulated emission cross-section for present glasses having 4F9/2 → 6H13/2 transition. The decay measurement for all the glass samples were recorded with an excitation at 350 nm and monitoring emission at 575 nm corresponding to the 4F9/2 → 6H13/2 transition and decay curves were fitted to bi-exponential fit. The CIE colour chromaticity coordinates were determined using CIE chromaticity diagram and the values were found to be in close proximity with the standard white light (0.33. 0.33) for all the glasses. Further colour correlated temperature values were found to lie in the near bright white region with CCT around ~4000 K.