Novel Red-Emitting Ba2Tb(BO3)2Cl:Eu Phosphor with Efficient Energy Transfer for Potential Application in White Light-Emitting Diodes

A novel red-emitting Ba2Tb(BO3)(2)Cl:Eu phosphor possessing a broad excitation band in the near-ultraviolet (n-UV) region was synthesized by the solid-state reaction. Versatile Ba2Tb(BO3)(2)Cl compound has a rigid open framework, which can offer two types of sites for various valence's cations to occupy, and the coexistence of Eu2+/Eu3+ and the red-emitting luminescence from Eu3+ with the aid of efficient energy transfer of Eu2+-Eu3+(Tb3+) and Tb3+-Eu3+ have been investigated. Ba2Tb(BO3)(2)Cl emits green emission with the main peak around 543 nm, which originates from D-5(4) --> F-7(5) transition of Tb3+. Ba2Tb(BO3)(2)Cl:Eu shows bright red emission from Eu3+ with peaks around 594, 612, and 624 nm under n-UV excitation (350-420 nm). The existence of Eu2+ can be testified by the broad-band excitation spectrum, UV-vis reflectance spectrum, X-ray photoelectron spectrum, and Eu L-3-edge X-ray absorption spectrum. Decay time and time-resolved luminescence measurements indicated that the interesting luminescence behavior should be ascribed to efficient energy transfer of Eu2+-Eu3+(Tb3+) and Tb3+-Eu3+ in Ba2Tb(BO3)(2)Cl:Eu phosphors.