Photoluminescence properties of color-tunable SrMgAl10O17:Eu2+,Mn2+ phosphors for UV LEDs

Aluminate phosphors SrMgAl10O17 codoped with Eu2+ and Mn2+ ions were prepared by solid-state reaction. The phase structure and photoluminescence properties of the as-prepared phosphors were characterized by powder X-ray diffraction, photoluminescence excitation and emission spectra. Upon excitation of UV light, two broad emission bands centered at 470 and 515 nm were observed, and they were assigned to Eu2+ and Mn2+ emissions, respectively. The emission color of the phosphors can be tuned from blue to cyan and finally to green by adjusting the concentration ratios of Eu2+ and Mn2+. Effective energy transfer occurs from Eu2+ to Mn2+ in the host due to the spectral overlap between the emission band of Eu2+ and the excitation bands of Mn2+. The energy transfer mechanism was demonstrated to be electric dipole-quadrupole interaction. The energy transfer efficiency and critical distance were also calculated. The phosphors exhibit strong absorption in near UV spectral region and therefore they are potentially useful as UV-convertible phosphors for white LEDs. (C) 2012 Elsevier B.V. All rights reserved.