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

Highlights: • Ba₂Gd₅B₅O₁₇:Ce³⁺/Tb³⁺ borate phosphors were prepared for the first time. • Crystal structure and luminescence properties were studied. • Efficient energy transfer from Ce³⁺ to Tb³⁺ ions took place. • Blue-green color-tunable emissions were realized upon 345 nm excitation. • Thermal stability was investigated. 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.