Synthesis and photoluminescence properties of Ce3+ and Tb3+ doped Na3Gd(PO4)2 phosphors for white LEDs

Na 3 Gd(PO 4 ) 2 phosphors doped with rare-earth metal ions Ce 3+ and Tb 3+ were fabricated by the solid-state reaction method. Under the excitation of 340 nm light, the Ce 3+ -doped Na 3 Gd(PO 4 ) 2 phosphors exhibit a broad emission band ranging from 370 nm to 480 nm, which emitted blue light centered at 405 nm. When excited at 373 nm, the Tb 3+ -doped Na 3 Gd(PO 4 ) 2 phosphors presented a green light emission, including a strong peak located at 547 nm. In addition, both of the Na 3 Gd(PO 4 ) 2 : Ce 3+ and Na 3 Gd(PO 4 ) 2 : Tb 3+ phosphors showed excellent thermal stability at different temperatures, be specific in the Na 3 Gd(PO 4 ) 2 : Ce 3+ emission intensities at 150 °C could maintain about 84 % and the Na 3 Gd(PO 4 ) 2 : Tb 3+ could maintain about 92.9 % of those at room temperature. A prototype of the white light-emitting diodes lamp exhibiting bright white light was fabricated by using a 365 nm near-ultraviolet-emitting LED chip, combined with Na 3 Gd(PO 4 ) 2 : Ce 3+ blue phosphors, Na 3 Gd(PO 4 ) 2 : Tb 3+ green phosphors, and Na 3 Gd(PO 4 ) 2 : Eu 3+ red phosphors , which produced a high color rendering index of 89.4, and a relatively low correlated color temperature of 5496 K. Moreover, the CIE point was calculated to be at (0.3332, 0.3438), locating in the white light region. These results indicate that the as-prepared phosphors can be considered as potential candidates for ultraviolet/near-ultraviolet light-excited white light-emitting diodes applications.