Near ultraviolet excitable cyan-green phosphors of Ba 6 La 2 Al 3 ScO 15 :Ce 3+ and Ba 6 La 2 Al 3 ScO 15 :Ce 3+ ,Tb 3+ : investigations on the crystal structure, site assignment of Ce 3+ and Tb 3+ ions, and an energy transfer process from Ce 3+ to Tb 3 .

An energy transfer from Ce 3+ to Tb 3+ is feasible in energy transition processes for the development of optical devices, especially phosphor-converted white LEDs (pc-wLEDs). Most of the energy transfer phosphors co-doped with Ce 3+ and Tb 3+ , unfortunately, have weak absorption under a near-ultraviolet light of around 405 nm and blue light excitation, making them incapable for use as near ultraviolet or blue LEDs. In this study, novel energy transfer luminescent materials, Ba 6 La 2 Al 3 ScO 15 :Ce 3+ ,Tb 3+ , isostructural with existing Ba 6 La 2 (Al,Fe) 4 O 15 , were successfully synthesized through a conventional solid-state reaction as a single phase. The phosphors showed a broad cyan emission of Ce 3+ and narrow green emissions of Tb 3+ under a near-ultraviolet light of 405 nm, which was nearly located at an emission wavelength of near-ultraviolet LEDs. The occurrence of energy transfer from Ce 3+ to Tb 3+ was evidenced by emission lifetime measurements. The lifetime analysis based on formulated energy transfer models, such as Inokuti-Hirayama, Yokota-Tanimota and Martin models, revealed that an energy transfer process from Ce 3+ to Tb 3+ took place dominantly by a dipole-dipole interaction with low migration among the donors of Ce 3+ .