Blue-Emitting K2Al2B2O7:Eu2+ Phosphor with High Thermal Stability and High Color Purity for Near-UV-Pumped White Light-Emitting Diodes

Novel blue-emitting K2Al2B2O7:Eu2+ (KAB:Eu2+) phosphor was synthesized by solid state reaction. The crystal structural and photoluminescence (PL) properties of KAB:Eu2+ phosphor, as well as its thermal properties of the photoluminescence, were investigated. The KAB:Eu2+ phosphor exhibits broad excitation spectra ranging from 230 to 420 nm, and an intense asymmetric blue emission band centered at 450 nm under lambda(ex) = 325 nm. Two different Eu2+ emission centers in KAB:Eu2+ phosphor were confirmed via their fluorescence decay lifetimes. The optimal concentration of Eu2+ ions in K2-xEuxAl2B2O7 was determined to be x = 0.04 (2 mol %), and the corresponding concentration quenching mechanism was verified to be the electric dipoledipole interactions. The PL intensity of the nonoptimized KAB:0.04Eu(2+) phosphor was measured to be similar to 58% that of the commercial blue-emitting BaMgAl10O17:Eu2+ phosphor, and this phosphor has high color purity with the CIE coordinate (0.147, 0.051). When heated up to 150 degrees C, the KAB:0.04Eu(2+) phosphor still has 82% of the initial PL intensity at room temperature, indicating its high thermal stability. These results suggest that the KAB:Eu2+ is a promising candidate as a blue-emitting n-UV convertible phosphor for application in white light emitting diodes.