Czochralski Growth and Characterization of a Compositionally Complex Rare Earth Aluminum Garnet Scintillator: (Gd_1/4Y_1/4Tb_1/4Lu_1/4)₃Al<sub>5</sub

Compositionally complex oxides have garnered increasing interest for their enhanced phase stability and tunable functional properties, yet their development as bulk single crystal scintillators remains limited. Herein, we report the Czochralski growth and characterization of (Gd_1/4Y_1/4Tb_1/4Lu_1/4)₃Al₅O₁₂:Ce (GYTLAG), a compositionally complex garnet incorporating four dodecahedrally coordinated principal rare earth elements. The garnet phase was confirmed by powder and single crystal X-ray diffraction, and macroscopic defects are described. X-ray absorption near-edge structure measurements confirm the 3+ oxidation state of all rare earths and support their occupation of the same crystallographic site; white line intensity variations correlate with the anticipated segregation behavior. Elemental segregation is quantified by SEM/EDS and ICP-OES, and a linear trend was established between the segregation coefficient and the difference between each rare earth’s ionic radius (r) and the average ionic radius (AIR) of the dodecahedral site. This trend offers a predictive framework for compositional control in future REAG crystals grown by the Czochralski method. Photoluminescence and radioluminescence measurements reveal both Ce³⁺ and Tb³⁺ emission. Scintillation pulses exhibit four-component decay with dominant ~230 µs and ~1.2 ms components, and the light yield is estimated to be up to 43,000 ph/MeV under 137Cs γ-ray excitation. GYTLAG also demonstrates a strong radioluminescence efficiency and 50% lower afterglow at 20 ms compared to a LuAG:Ce reference, underscoring its promise for scintillator applications.. Authors: Lalk, Rebecca [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN, 37996; Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN, 37996] (ORCID:0000000169936438); van Veelen, Arjen [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545]; Tratsiak, Yauhen [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN, 37996]; Rutherford, Aya [Department of Physics, University of Tennessee Knoxville, TN, 37996]; Koehler, Michael [IAMM Diffraction Facility, University of Tennessee Knoxville, TN, 37996]. DOE Contract: NA0003996. Subjects: Compositionally complex oxide, high entropy oxide, Czochralski, segregation, garnet, scintillator