Activator segregation and micro-luminescence properties in GAGG: Ce ceramics

BBCeramic scintillators are promising due to their potentially low cost. Here, we report on our study of Ce-doped ceramics. Typical garnet-type ceramics Gd2.97Ce0.03Al2Ga3O12 was fabricated for the study from co-precipitated powders by high-temperature sintering in air. Its structure and composition are characterized using Scanning Electron Microscope (SEM) imaging, Transmission Electron Microscopy (TEM), Electron Energy Loss Spectroscopy (EELS), Electron Backscattered Diffraction (EBSD) mapping, X-Ray Diffraction (XRD) and X-ray Absorption Near Edge Structure (XANES) measurements. The spatial distribution of luminescence properties at the microlevel is studied using scanning confocal microscopy. Cerium segregation at the grain boundaries was revealed by compositional characterization and is in line with enhanced Ce3+ photoluminescence observed at the boundaries. Meanwhile, no excess partitioning of Ce4+ ions at the grain boundaries is observed. It is found that most of Ce ions in the ceramics are stabilized in the state Ce3+, what is encouraging in view of the further development of GAGG:Ce ceramics as a promising luminescence material for lighting and scintillator application.