Photoluminescence properties of novel Ba2Lu5B5O17:Eu3+ red emitting phosphors with high color purity for near-UV excited white light emitting diodes.

Abstract

A series of new red-emitting Ba2Lu4.98−xEuxLa0.02B5O17 (0.1 ≤ x ≤ 1.0) phosphors were synthesized via the high-temperature solid-state reaction method. The phase formation of the as-synthesized Ba2Lu4.48Eu0.5La0.02B5O17 phosphor was confirmed by powder X-ray diffraction analysis. It was found that La3+ doping resulted in the reduction of LuBO3 impurities and thus pure phase Ba2Lu5B5O17 was realised. The morphology of Ba2Lu4.48Eu0.5La0.02B5O17 phosphors was studied by field emission scanning electron microscopy (FE-SEM). As a function of Eu3+ concentration the photoluminescence spectra and decay lifetimes were investigated in detail. Under excitation at 396 nm, a dominant red emission peak located at 616 nm (5D0 → 7F2) indicated that Eu3+ ions mainly occupied low symmetry sites with a non-inversion center in Ba2Lu4.48Eu0.5La0.02B5O17. The optimal Eu3+ ion concentration was found to be x = 0.5 and the critical distance of Eu3+ was determined to be 6.55 Å. In addition, the concentration quenching takes place via dipole–dipole interactions. The phosphors exhibited good CIE (Commission International de I'Eclairage) color coordinates (x = 0.643, y = 0.356) situated in the red region and a high color purity of 97.8%. Furthermore, the internal quantum efficiency and the thermal stability of Ba2Lu4.48Eu0.5La0.02B5O17 phosphors were also investigated systematically. The results suggest that Ba2Lu4.48Eu0.5La0.02B5O17 may be a potential red phosphor for white light-emitting diodes.