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.