Karol Bartosiewicz, Justyna Zeler, Marcin E Witkowski, Masao Yoshino, Robert Tomala, Om Prakash, Damian Szymanski, Maksym Buryi, Aleksandra Owczarek, Andrey Prokhorov, Vítězslav Jarý, Kei Kamada, Pietro Galinetto, Winicjusz Drozdowski, Eugeniusz Zych, Akira Yoshikawa, Gongxun Bai
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.