Energy transfer induced color-tunable emissions from Ba2Gd5B5O17:Ce3+/Tb3+ borate phosphors for white LEDs

Abstract

In this paper, Ce3+/Tb3+ co-doped blue-green emitting Ba2Gd5B5O17 borate phosphors were prepared for the first time. Phase purity, crystal structure, photoluminescence properties, energy transfer, and thermal stability of the as-synthesized samples were studied in detailed. The Ce3+ ions singly doped Ba2Gd5B5O17:Ce3+ phosphors had a broad excitation band in the 300–400 nm spectral range peaking at 345 nm, and when excited at 345 nm they exhibited a broad blue emission band in the 350–700 nm wavelength range with a maximum at 450 nm. Energy transfer process from Ce3+ to Tb3+ ions took place in the Ce3+/Tb3+ co-doped Ba2Gd5B5O17 phosphors, resulting in color-tunable emission outputs. It was found that under the excitation of 345 nm, the emission spectra of Ba2Gd5B5O17:Ce3+,Tb3+ phosphors displayed the broad blue emission band of Ce3+ ions and the characteristic sharp green emission lines of Tb3+ ions. Moreover, the intensity ratio of Ce3+ blue emission to Tb3+ green emission was adjusted by increasing the Tb3+ doping concentration, and the Ce3+→Tb3+ energy transfer mechanism was studied. Furthermore, the thermal stability of Ba2Gd5B5O17:Ce3+,Tb3+ phosphors was estimated, and the activation energy of Ba2Gd5B5O17:0.008Ce3+,0.2 Tb3+ sample was calculated to be 0.205 eV. The obtained results revealed that blue-green emitting Ba2Gd5B5O17:Ce3+,Tb3+ borate phosphors have potential usage in the fabrication of near-UV based white LEDs.