Evaluating the link between blue-green luminescence and cross-relaxation processes in Tb3+-doped glasses

In this study, luminescence properties of Tb3+-doped low silica calcium aluminosilicate glasses are analyzed as a function of Tb3+ concentration (0.04-15.0 wt%). Decay curves for the D-5(3) level are found to be non-exponential for all Tb3+ concentrations due to ion-ion energy transfer through cross-relaxation process. To identify the origin of the energy transfer mechanism, the decay curves were well fitted by Inokuti-Hirayama model (s = 6), which indicates that the energy transfer process is related to dipole-dipole interaction. Trivalent Tb-doped materials normally exhibit stronger green emission compared to blue emission, a feature that increases with Tb3+ concentration and is attributed to the cross-relaxation process. In this paper, we show a remarkable blue emission in comparison to other Tb3+-doped glasses. A theoretical model for the blue and green emissions, from D-5(3) and D-5(4) levels respectively, was proposed to establishing a link between the color emission and the D-5(3) lifetime quenching due to a cross-relaxation process. This model was successfully applied to the experimental results of this paper as well as previous data in the literature.