Yellow-emitting (Tb 1−x Ce x ) 3 Al 5 O 12 phosphor powder and ceramic (0≤x≤0.05): Phase evolution, photoluminescence, and the process of energy transfer

Abstract (Tb 1 -x Ce x ) 3 Al 5 O 12 yellow phosphors (0≤x≤0.05) were calcined from their coprecipitated carbonate precursors, and the effects of the temperature and atmosphere (air and H 2 ) 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 H 2 /Ar gas mixture at the relatively low temperature of 1500 °C. The phosphors simultaneously exhibit the 4f 8 →4f 7 5d 1 , 7 F 6 → 5 D 3 and 7 F 6 → 5 D 4 excitations of Tb 3+ and the 4f 1 →5d 1 excitation of Ce 3+ when monitoring the yellow emission of Ce 3+ at 560 nm, suggesting the presence of efficient Tb 3+ →Ce 3+ energy migration. The optimal Ce 3+ content for luminescence was found to be x =0.015 and 0.01 under the direct excitation of Ce 3+ and through Tb 3+ →Ce 3+ 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 Ce 3+ content, with an in-depth discussion on the process of energy transfer among the optically active Tb 3+ and Ce 3+ ions. The materials may find application in blue-light excited white LEDs.