Structural and optical studies on Dy3+:Tb3+ co-doped zinc leadfluoro-borophosphate glasses for white light applications

A new series of Dy3+:Tb3+ co-doped zinc leadfluoro-borophosphate glasses were prepared by varying Tb3+ ions concentration through melt quenching technique. Influence of Tb3+ ions concentration on the structural and spectroscopic properties of Dy3+:Tb3+ co-doped title glasses were explored through FTIR, Raman, optical absorption, luminescence and decay measurements. The phonon vibrational energy of the chosen glass host is found to be 998 cm−1 through Raman spectrum. Dy3+ ions act as sensitizer to Tb3+ ions emission which originates from the 5D4 metastable state of Tb3+ ions through non-radiative energy transfer with a maximum efficiency of 44%. At higher Tb3+ ions concentration, the 4F9/2 metastable state of the Dy3+ ions can also be mutually sensitized by Tb3+ ions which inturn increases the lifetime of the 4F9/2 state of Dy3+ ions. Nature of energy transfer in both the cases was investigated through Dexter's energy transfer mechanism and Inokuti-Hirayama (IH) model. These results suggest that dipole-dipole type of interaction is responsible for Dy3+ to Tb3+ energy transfer and dipole-quadrupole interaction is responsible for Tb3+ to Dy3+ energy transfer. The characteristic emission color of the prepared glasses were examined through CIE 1931 chromaticity coordinates and the corresponding correlated color temperature (CCT) values were estimated which indicates the possible neutral white light emission from the title glasses. All these studies concludes that 0.25 wt% Tb3+ ions co-doped 0.5 wt% Dy3+ ions incorporated titled glass is more suitable for neutral white light emitting applications.