Scandium and aluminum substitution and energy transfer processes in the undoped and Ce-doped ▫$Y_{3}Sc_{?}Al_{5−?}O_{12}$▫ scintillation crystals

The structural and scintillation properties of pure and Ce-doped Y3⁢Sc�⁢Al5−�⁢O12 (�=0, 0.05, 1.16, and 2) crystals were systematically investigated. High-resolution 45 Sc and 27 Al magic angle spinning nuclear magnetic resonance spectroscopy revealed that S⁢c3+ ions predominantly occupy octahedral sites, effectively replacing A⁢l3+ ions, while antisite Sc at Y dodecahedral positions remains below 0.2 at.%. Sc incorporation into Y3⁢Al5⁢O12 induces strong exciton emission at 320–324 nm, nearly 10 times higher than that of reference Bi4⁢Ge3⁢O12 (BGO) crystal, even at low Sc concentrations (5 at.%). C⁢e3+ doping introduces characteristic 5⁢�1→4⁢� emission at 518 nm, accelerates scintillation decay, and in combination with M⁢g2+ codoping, promotes the formation of C⁢e4+ ions that enable a fast radiative de-excitation pathway. Y3⁢Sc2⁢Al3⁢O12: Ce exhibits a maximum scintillation light yield of 80–84% relative to BGO with a mean decay time of 85–110 ns. Thermostimulated liminescence and electron paramagnetic resonance studies indicate that holes are mainly trapped at oxygen ions near Sc ions (O− centers), while electrons are primarily localized at Sc antisite ions near oxygen vacancies (S⁢c2+–VO centers), affecting scintillation kinetics. Density functional theory calculations confirm that S⁢c3+ at the dodecahedral site forms a deep electron trap. These results highlight the key role of Sc and Ce in tuning emission, decay dynamics, and defect-mediated processes in Sc-admixed multicomponent garnet scintillators.