Yellow-emitting (Tb1−xCex)3Al5O12 phosphor powder and ceramic (0≤x≤0.05): Phase evolution, photoluminescence, and the process of energy transfer

(Tb1-xCex)3Al5O12 yellow phosphors (0≤x≤0.05) were calcined from their coprecipitated carbonate precursors, and the effects of the temperature and atmosphere (air and H2) of calcination on the sequence of phase evolution and the characteristics of the powders were investigated in detail. The activation energy for the crystallite growth during calcination was estimated to be ~39 kJ/mol. The powder calcined at 1000 °C showed good reactivity and was sintered into a ceramic plate of ~97% dense (average grain size: ~1.3 µm) in a H2/Ar gas mixture at the relatively low temperature of 1500 °C. The phosphors simultaneously exhibit the 4f8→4f75d1, 7F6→5D3 and 7F6→5D4 excitations of Tb3+ and the 4f1→5d1 excitation of Ce3+ when monitoring the yellow emission of Ce3+ at 560 nm, suggesting the presence of efficient Tb3+→Ce3+ energy migration. The optimal Ce3+ content for luminescence was found to be x=0.015 and 0.01 under the direct excitation of Ce3+ and through Tb3+→Ce3+ energy transfer, respectively, and concentration quenching of luminescence was analyzed to be resulted from exchange interaction. Luminescence features of the phosphors, including excitation, emission, quantum yield, fluorescence lifetime, color coordinates and color temperature, were thoroughly investigated against the processing temperature and Ce3+ content, with an in-depth discussion on the process of energy transfer among the optically active Tb3+ and Ce3+ ions. The materials may find application in blue-light excited white LEDs.