Synthesis and photoluminescence characteristics of high color purity Ba 3 Y 4 O 9 :Eu 3+ red-emitting phosphors with excellent thermal stability for warm W-LED application.

Single phase Eu 3+ -activated Ba 3 Y 4 O 9 (Ba 3 (Y 1- x Eu x ) 4 O 9 ) red-emitting phosphors with different Eu 3+ doping concentrations were synthesized by a high temperature solid-state reaction method. The phase purity, crystal structure, photoluminescence properties, internal quantum efficiency, decay lifetimes, and thermal stability were investigated. Upon excitation at 396 nm near-ultraviolet light and 469 nm blue light, the Ba 3 (Y 1- x Eu x ) 4 O 9 phosphors exhibited a strong red emission at 614 nm due to the 5 D 0 → 7 F 2 transition of Eu 3+ ions. The optimal doping concentration of Eu 3+ ions in Ba 3 (Y 1- x Eu x ) 4 O 9 was found to be x = 0.25. Furthermore, the critical distance was calculated to be 12.78 Å and the energy transfer mechanism for the concentration quenching effect was determined to be quadrupole-quadrupole interaction. In addition, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates of Ba 3 (Y 0.75 Eu 0.25 ) 4 O 9 phosphors were measured to be (0.6695, 0.3302) which located at the red region, and significantly, the high color purity was about 97.9%. The as-synthesized phosphors also possessed excellent thermal stability and the activation energy was determined to be 0.29 eV. Therefore, the investigated results indicated that the Ba 3 Y 4 O 9 :Eu 3+ phosphor may be a suitable candidate as a red phosphor for white light-emitting diodes under effective excitation at near-ultraviolet and blue light.