Yttrium Oxide-Deficient Melts Control Secondary-Phase Distribution in Cerium-Doped Terbium-Yttrium Aluminum Garnet...

Controlled melt nonstoichiometry was investigated as a processing parameter governing secondary-phase formation and functional properties of Ce³⁺-doped (Tb,Y)₃Al₅O₁₂ single crystals grown by micropulling-down. Crystals were grown from melts with 0, 3, 6, 9, and 11 mol % Y₂O₃ deficiency. X-ray diffraction, electron probe microanalysis, and Raman spectroscopy revealed phase-pure garnet up to 3 mol % deficiency, rim-localized α-Al₂O₃ inclusions at 6 and 9 mol %, and core-localized perovskite-type inclusions at 11 mol %. Secondary-phase formation modified Tb/Y partitioning in the garnet matrix, affecting Ce³⁺ emission kinetics, Tb³⁺↔Ce³⁺ energy transfer, trap depth, and scintillation properties. The 11 mol % deficient crystal showed the highest thermal stability, with the Ce³⁺ thermal-quenching onset shifting from 375 to 425 K. The 9 mol % deficient crystal reached a luminous efficacy of 158 lm/W and a scintillation light yield of 33,600 photons/MeV. X-ray radiography using the 9 mol % Y₂O₃-deficient crystal showed clear images of an SD card. These results indicate that melt nonstoichiometry can tune the balance between photoconversion and scintillation performance in rare-earth garnets.