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This study provided the first in-depth investigation of the effects of large dopant incompatibility (Pr3+ and La3+ ions) on the small host lattice element (Lu3+) in Lu 3 Al 5 O 12 (LuAG) single crystal. The growth of such complex crystals from the melt presented many challenges. By engineering the ionic radius ratio of RE- and M-site cations, a single-crystal phase stabilized by configurational entropy was achieved. This investigation elucidated the crystallization behavior of configurationally disordered rare-earth aluminum garnet oxide (Lu 1−x−y Pr x La y) 3 Al 5 O 12 from the melt and characterized its functional properties, including microstructural, optical, photoluminescence, and scintillation properties, between 5 and 300 K. Relaxation of the imposed strain energy led to local perturbations and destabilization of the garnet structure. Multielemental EDS mapping, micro-Raman spectroscopy, and thermoluminescence revealed the mechanism by which atomic size mismatch drove a smooth transition from the garnet to the perovskite phase in high entropy garnets. The optical, photoluminescence, and scintillation measurements provided fundamental insights into property changes driven by incompatibility doping. Standard and modified Judd-Ofelt theory analysis of absorption spectra determined the phenomenological Judd-Ofelt parameters Ω λ and radiative lifetimes. Atomic size mismatch engineering offers a promising approach to overcoming the limitations of conventional eutectic synthesis methods. • Perovskite inclusions, driven by atomic size mismatch, extend from rim to core. • Controlled incompatible La3+,Pr3+ codoping in LuAG modify functional properties. • Scintillation light yield improved up to 30% in La3+ codoped LuAG:Pr crystals. • (La,Pr)AlO 3 perovskite forms due to size mismatch of La3+ and Pr3+ with Lu3+. • Lattice disorder affects the intensity ratio of Pr³⁺ 5d→4 f and 4 f→4 f emissions. [ABSTRACT FROM AUTHOR]

High-quality lutetium aluminum garnet doped with various Pr3+ concentrations ((Lu 1- x Pr x) 3 Al 5 O 12 , abbreviated to Pr:LuAG) single crystals were grown by the optical floating zone method. The concentration of Pr3+ dependence on microstructure, luminescence and scintillation properties were systematically studied. Based on the results of Rietveld refinement, the doping of Pr3+ leads to lattice distortion and lowers its symmetry. The symmetry of the LuO 8 dodecahedron center is lowest at 0.010, as confirmed by the Raman spectra. When excited at 450 nm and X-rays, the primary emission peak at 614 and 300 nm, respectively, induced by Pr3+ 4 f 2-4 f 2 and 4 f 5 d -4 f 2 transitions. The optimal doping concentration is 0.010. The electric dipole-electric dipole interaction between adjacent Pr3+ was responsible for the concentration quenching in the Pr:LuAG single crystals. (Lu 0.990 Pr 0.010) 3 Al 5 O 12 shows the shortest average scintillation decay time (22.55 ns) and highest light yield (23,842 ± 2300 ph./MeV) under 662 KeV 137Cs gamma-ray irradiation. In terms of overall luminescence and scintillation performance, 0.010 doping was the best for Pr3+ doped LuAG single crystals. • High quality Pr:LuAG single crystal was grown by optical floating zone method. • Pr ions lead to the enhanced translational motion of rare earth ions in Pr:LuAG. • Electric dipole-electric dipole interaction induced concentration quenching of Pr3+. • 0.010 Pr:LuAG single crystal has the best scintillation and luminescence properties. [ABSTRACT FROM AUTHOR]

This study concerns cerium and boron doped Lu 3 Al 4 Sc 1 O 12 and Gd 3 Al 3 Sc 2 O 12 garnet µ-crystalline powders, which were synthesized for the first time. Rare earth ion, particularly Ce3+ activated garnets, due to their high density and efficient Ce3+ luminescence upon blue, UV, or x-ray excitation, can be used as scintillators that convert high-energy radiation into visible light. The incorporation of B3+ and Sc3+ ions into the garnet matrix corresponds to the improvement of the scintillating properties. Boron in these compounds could act like a flux and thus modulate particle morphology, while scandium solely changes the physical and luminescent properties of these garnets. From the measured radioluminescence emission spectra, it could be concluded that boron doping results in a higher emission intensity when the compounds are excited by high-energy radiation. The most striking effect is that the decay time is reduced, and the quantum efficiency of the compounds increases. After improving the kinetic properties of these compounds, it is possible to discuss a wider application of the synthesized materials. In addition to the aforementioned properties, room temperature as well as temperature dependent photoluminescence emission, excitation, and decay times at different temperatures were taken for all samples. The elemental composition of the samples was determined by using the ICP-OES technique. The crystal structure was analyzed by means of powder XRD. Particle morphology and size distribution were also investigated. The main idea of this research is to synthesize new and adjusted garnet type compounds that show better luminescent properties, which are required for scintillator materials. • Pure B3+ and Sc3+ co-doped LuAG:Ce and GdAG:Ce were synthesized by Sol-Gel method. • Reflectance spectra indicated about good quality of synthesized compounds. • Boron doping led to an increase in radio/photo luminescence intensities. • A reduction in decay times was caused by B3+ and Sc3+ co-doping. • Co-doping with B3+ led to an increase in quantum efficiency. [ABSTRACT FROM AUTHOR]

• Mg2+ codoping effect on the atoms segregation in GAGG:Ce single crystal studied. • The formation of defects in Mg2+ and Ce3+ codoped GAGG crystals discussed. • The luminescence quenching mechanism in Mg2+ codoped proposed. • The charge compensation mechanism discussed. • Mg2+ codoping influence on the scintillation and luminescence properties investigated. The undoped, Mg2+ doped, Ce3+ doped as well as Mg2+:Ce3+ codoped Gd 3 Al 2 Ga 3 O 12 crystals were grown from the melt by the micro-pulling down method. Ce3+ and Mg2+ ions were codoped in a wide concentration range. A study of Mg2+ ion concentration effect on the luminescence and scintillation properties as well as segregation of atoms and defects creation processes were carried out. Mg2+ doping in Gd 3 Al 2 Ga 3 O 12 led to the creation of O O • defects localized next to Mg2+ sites due to charge imbalance compensation. Consequently, neutral (Mg Ga/Al/Gd O O) x defects were formed. In Ce3+ doped crystals, Mg2+ codoping changed the valence state from Ce3+ to Ce4+ to maintain charge neutrality. Hence, additional neutral (Ce Gd • -Mg Ga/Al/Gd ′) x and (Ce Gd -Mg Ga/Al/Gd O O) x defects appeared. Moreover, Mg2+ induced charge imbalance in GAGG crystal might also be compensated by the formation of oxygen vacancies (V O •• ). The Mg2+ ions imposed defects deteriorated the segregation of atoms. Accordingly the radial inhomogeneity of the crystals was diminished. The presence of stable Ce4+ and defects imposed by Mg2+ ions codoping were proved by absorption, photoluminescence, and scintillation decay time analysis. Hence, Mg2+ codoping resulted in quenching of the Ce3+ luminescence, acceleration of scintillation response, reduction of light yield, and thermally stimulated luminescence. The mechanism explaining a strong luminescence quenching with increasing Mg2+ ions concentration was proposed. [ABSTRACT FROM AUTHOR]

• Machine learning models for scintillator performance require self-consistent data. • High-throughput screening needs a universal preparation technique. • Multi-component aluminate garnets were synthesized by quenching of the melt. • Structural and luminescence properties of powder samples were evaluated. • A simplified model was developed for interpretation of radioluminescence intensity. Quenching from the melt using an Optical Floating Zone furnace was investigated as a possible high-throughput preparation method in order to screen novel scintillating materials. To validate this method, polycrystalline rare-earth aluminum garnets and yttrium gallium aluminum garnets were synthesized and characterized by X-ray diffraction, photoluminescence and radioluminescence emission spectra as well as radioluminescence imaging and compared to the previously reported properties of those materials. In order to achieve rapid, but quantitative comparison of the materials, pellets fabricated from the synthesized powders were sintered; two different sintering conditions were investigated and compared. A simplistic energy deposition and light absorption model for brightness of opaque samples under X-ray irradiation was developed to estimate the relative scintillation efficiency of the materials. Based on the results, Y 3 Al 5 O 12 , LuY 2 Al 5 O 12 and GdY 2 Al 5 O 12 seem to have the highest scintillation efficiency among the prepared samples. [ABSTRACT FROM AUTHOR]