Scintillators are materials that emit light when exposed to high-energy radiation and are widely used in medical imaging and radiation detection. In this study, we compared two types of single crystals derived from Y3Al5O12 garnet: one doped with scandium (Sc) and the other with gallium (Ga), both also containing cerium (Ce), which secures light output.
Although both types were grown under controlled conditions, the gallium-based crystal significantly outperformed the scandium-based ones in light yield—producing over twice as much light. The best Sc-doped crystal reached 17.320 photons per MeV, while the Ga-doped one achieved 42.760 photons per MeV.
The reason lies in the crystal structure. In Sc-doped crystals, scandium ions often occupy positions normally reserved for gadolinium. These so-called "antisite defects" create deep electron traps, where electrons become stuck and can't contribute to light emission. This was confirmed through various experiments and band structure quantum calculations.
Despite the similar shift in conduction band energy levels in both types of crystals, the intrinsic formation of deep traps in Sc-doped garnets significantly limits their scintillation efficiency. These findings help explain performance differences and provide valuable insight for developing better-performing scintillator materials in the future.