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

Abstract

Na3Gd(PO4)2 phosphors doped with rare-earth metal ions Ce3+ and Tb3+ were fabricated by the solid-state reaction method. Under the excitation of 340 nm light, the Ce3+-doped Na3Gd(PO4)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 Tb3+-doped Na3Gd(PO4)2 phosphors presented a green light emission, including a strong peak located at 547 nm. In addition, both of the Na3Gd(PO4)2: Ce3+ and Na3Gd(PO4)2: Tb3+ phosphors showed excellent thermal stability at different temperatures, be specific in the Na3Gd(PO4)2: Ce3+ emission intensities at 150 °C could maintain about 84 % and the Na3Gd(PO4)2: Tb3+ 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 Na3Gd(PO4)2: Ce3+ blue phosphors, Na3Gd(PO4)2: Tb3+ green phosphors, and Na3Gd(PO4)2: Eu3+ 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.