Luminescence and chromaticity of alkaline earth aluminate MxSr1−xAl2O4:Eu2+ (M: Ca,Ba)

In order to prepare fluorescent material for UV-LED used as illumination light source, two series of Eu2+ doped (1 mol%) alkaline earth aluminate phosphors CaxSr1−xAl2O4 and BaxSr1−xAl2O4 were prepared. The crystal structure, relative quantum efficiency(Qr), peak wavelength(λp), color tuning and chromaticity were investigated by XRD patterns and photoluminescence (PL) on samples prepared by solid solution system (s series) and powder mixing system (m series) respectively. For the s series, the synthesized CaxSr1−xAl2O4:Eu2+ powders show that the structure transforms from monoclinic to hexagonal at x⩽0.5, and λp increases from 442.3 to 529.7 nm with decreasing x. For the BaxSr1−xAl2O4:Eu2+ system, the structure transforms from monoclinic to hexagonal at x⩾0.3, and λp decreases from 520.5 to 502.2 nm continuously from x=0 to 1. The shift in λp could be explained by the crystal field effect, which is affected by different coulomb attractive forces due to the various fraction of alkaline earth cation in the host lattice. Different phosphor properties prepared by either solid solution or powder mixing methods were characterized by chromaticity measurements for both reflective and transmissive modes.