Gd3+ Synergistic Sensitization in Tb3+-Doped LBSO Glasses: Influence of Cluster Dispersion and Energy Transfer on Luminescence and X-ray Detection
Gd3+-sensitized Tb3+-based glasses are high light-yield scintillators. Energy transfer sensitization between Gd3+ and Tb3+ is well-recognized. Gd3+ ions are also found to typically modulate the interionic distances of Tb3+ ions; however, the mechanism why this effect enhances the latter’s photoluminescence still remains unclear. This work focuses on Gd3+, Tb3+ co-doped La2O3-B2O3-SiO2 (LBSO), first demonstrating Tb3+ clusters via spectroscopy. LBSO’s optimal Tb3+ single-doping concentration is 37%, rising to 50% with 20% Gd3+. The LBSO:20%Gd3+,50%Tb3+ sample exhibits a 542 nm emission intensity 2.22 times that of the 37%Tb3+ single-doped sample, 38% scintillation efficiency (vs. BGO), and >20 lp mm−1 X-ray resolution. The introduction of Gd3+ increases the interionic distance between Tb3+ ions within the clusters, thereby suppressing the concentration quenching effect and enhancing the fluorescence emission. We propose this mechanism as “cluster-dispersion sensitization effect”. This effect was further confirmed in other glass systems (LBSO:Lu3+, Tb3+, LBSO:Y3+, Tb3+, Bi-based:Lu3+, Tb3+, etc.). Spectroscopic analysis shows Gd3+-Tb3+ energy transfer efficiency up to 80%. In conclusion, Gd3+ synergistically enhances Tb3+ fluorescence via both effects. These findings not only fully elucidate the sensitization mechanism of Gd3+ ions in Gd3+, Tb3+ co-doped scintillating glasses but also provide new insights for researching the manipulation of activator ion clusters in luminescent materials. In search for novel scintillators, cluster-dispersion sensitization effect may greatly improve their spatial resolution via intrinsic architectures design in glasses, ceramics, thin films, and nanoparticles.