Influence of Tb3+ co-doping on luminescence and scintillation performance of Y1.70Gd1.25Al2.8Ga2.15O12:Ce,Tb garnet films

Abstract

In this study, Y_1.70Gd_1.25Al_2.8Ga_2.15O₁₂:Ce,Tb (YGAGG:Ce,Tb) single-crystalline films (SCFs) with Tb³⁺ co-doping concentrations of 0, 1, and 5 at.% were grown on Gd₃Al₂Ga₃O₁₂ single crystal substrate using the isothermal liquid phase epitaxy method. The photoluminescence, radioluminescence, and scintillation properties were systematically studied with the aim to enhance the integral radioluminescence intensity. The bidirectional energy transfer process between Tb³⁺ and Ce³⁺ ions was confirmed by means of photoluminescence spectra and decay kinetics measurements. Under soft X-ray excitation, YGAGG:Ce,Tb1% SCF exhibited the highest relative intensity of the Ce³⁺ emission and the highest integral radioluminescence yield of ∼180 % of Tb - free YGAGG:Ce one. Conversely, the scintillation light yield, measured within a few μs time gate under excitation with high-energy ionizing radiation, does not increase upon co-doping with Tb³⁺ ions. Under excitation with 5.5 MeV α-particles from a²³⁸Pu radioactive source, the scintillation light yield of 8750 photons/MeV and good energy resolution of 5.5 % obtained for the YGAGG:Ce SCF are better than the values obtained for the YGAGG:Ce,Tb1% one (6740 photons/MeV and 14.3%). High integral radioluminescence yield of this YGAGG:Ce,Tb1% SCF along with rather high onset temperature for thermal quenching of 362 K of the Ce³⁺-related emission makes it a promising scintillator for utilization in medical X-ray imaging devices. Due to the particularly high thermal stability of Tb³⁺-related emission up to ∼700 K the Tb-doped garnets are suitable for high-temperature applications.