Energy Transfer from Ce3+ to Tb3+/Dy3+/Mn2+ in Ca9Ga(PO4)7 Phosphors: Synthesis, Structure and Tunable Multicolor Luminescent Properties

A series of Ca9Ga(PO4)(7):Ce3+/Tb3+/Dy3+/Mn2+ phosphors with tunable color, in which Ce3+ acts as the sensitizer, was synthesized. Energy transfer (ET) from Ce3+ to Tb3+/Dy3+/Mn2+ was investigated in detail. Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)(7) can exhibit green, yellow, and red emission, respectively. Incorporating Ce3+ into a Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)(7) phosphor can remarkably promote the luminous efficiency of the Tb3+/Dy3+/Mn2+ ions. This enhancement originates from an efficient ET from Ce3+ to Tb3+/Dy3+/Mn2+. The ET was validated by luminescence spectra, decay dynamics, and schematic energy levels. Moreover, the intensity ratio of red emission of Mn2+ to violet emission of Ce3+ was analyzed based on energy-transfer and lifetime measurements. In Ce3+-Tb3+, Ce3+-Dy3+, and Ce3+-Mn2+ doped Ca9Ga(PO4)(7), the emitting color changed from violet to green, yellow, and red, respectively, which indicates the potential use of this new tunable phosphor in UV light-emitting diodes.