Fabrication and luminescence of Ce-doped GGAG transparent ceramics made by two-step reaction sintering

Ce-doped garnets find their use as scintillators as well as phosphors. Among synthetic garnets, gallium gadolinium aluminum garnet (GGAG) is a relatively new and interesting material, a mixed garnet that has displayed very good scintillation and luminescent properties [1]. In the presented work GGAG ceramic samples were produced by reaction sintering from commercial oxide powders. The mixed powders were pressed into pellets and sintered. In order to achieve transparency of a ceramic material, it is crucial to eliminate porosity. Therefore, the sintering process was carefully selected and the use of sintering additives was studied. The sintering process consisted of two steps, viz. sintering in air followed by hot isostatic pressing. The influence of starting powders, sintering additives and sintering conditions on the microstructure and optical quality of the ceramics was studied. Fig. 1 shows one of the ceramic samples and its microstructure. Luminescence properties were studied by means of photo- and radio-luminescence and correlated to the fabrication process parameters. In some of the samples, significant persistent luminescence was observed and studied. Moreover, point defects were investigated by thermally stimulated luminescence, also in comparison with a single crystal with the same composition. [1] Y. Wu, F. Meng, Q. Li, M. Koschan, C. L. Melcher. Role of Ce4+ in the scintillation mechanism of codoped Gd3Ga3Al2O12:Ce. Phys. Rev. Appl. 2 (2014) 044009.