Energy migration and scintillation kinetics in compositionally complex (Gd1/4Y1/4Tb1/4Lu1/4)3Al5O12:Ce single crystal scintillator

It is well-established that compositional tuning through binary admixture can improve scintillation performance in several materials systems, including Ce-activated garnets. Although recent work on ternary or quaternary cation admixture shows promise, the impact of this increased compositional complexity on thermal stability and carrier-defect dynamics has not been addressed. Here, we investigate a compositionally complex garnet, (Gd_1/4Y_1/4Tb_1/4Lu_1/4)₃Al₅O₁₂:Ce (GYTLAG), grown by the Czochralski method using temperature-dependent photoluminescence (PL), PL decay, and thermoluminescence (TL). PL and PL decay measurements support a thermally activated Tb³⁺-Ce³⁺ energy transfer, where Tb³⁺ emission dominates below 60 K, but Ce³⁺ emission increases from 20 to 300 K. Thermal quenching of Ce³⁺ emission occurs around T₅₀ = 508 K, with an activation energy of 0.6 eV. TL and wavelength-resolved TL spectra from 20 to 500 K show that GYTLAG contains similar trap groups to LuAG but with a broader distribution of glow peaks below room temperature, possibly caused by quaternary cation mixing. A combination of dose dependence, partial cleaning and initial rise, and glow curve fitting to a first order continuous Gaussian distribution model are used to understand the contribution of electronic point defects to scintillation decay and afterglow at room temperature. These results inform how increased compositional complexity influences recombination dynamics in garnet scintillators.