Concentration-dependent microstructure and luminescence dynamics of Sm^3 +-doped Gd₃Al₃Ga₂O₁₂ transparent ceramics for orange-red emission

Rare earth ion-doped gadolinium aluminum gallium garnet (GAGG) transparent ceramics are important materials used in optoelectronic devices. Among them, Sm³⁺ doping is an effective way to achieve high-purity orange-red luminescence. In this study, Gd_3-xAl₃Ga₂O₁₂:xSm³⁺ transparent ceramics were prepared by two-step atmosphere sintering strategy, and it was found that their microstructure and optical properties were not synchronized with the change of doping concentration. The experimental results show that the grain growth conditions are the best (the average size is about 9.66 μm) at the doping concentration x = 0.03, and the transmittance can reach 80% in the visible light range. Within the study range, ceramics with doping concentrations x = 0.05 exhibited the highest luminous intensity, at which the system did not undergo significant concentration quenching and exhibited bright orange-red emission with a color purity exceeding 99.8%. Based on the analysis of steady-state and transient luminescence spectra combined with Judd–Ofelt (J–O) theory, the radiative transition characteristics were evaluated in this study. Further analysis of the concentration-dependent decay kinetics indicated that the shortening of the decay time is associated with the enhanced energy migration among Sm³⁺ ions at higher concentrations. In addition, the thermal quenching barrier is 0.124 eV, which reflects the relevant thermal stability properties of ceramics. In this study, the luminescence kinetics of Sm³⁺ doped GAGG ceramics were sorted out and its application potential in display technology was verified.