Luminescence and chromaticity of alkaline earth aluminate M xSr 1−xAl 2O 4:Eu 2+ (M: Ca,Ba)

Abstract

In order to prepare fluorescent material for UV-LED used as illumination light source, two series of Eu 2+ doped (1 mol%) alkaline earth aluminate phosphors Ca x Sr 1− x Al 2O 4 and Ba x Sr 1− x Al 2O 4 were prepared. The crystal structure, relative quantum efficiency(Qr), peak wavelength( λ p ), 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 Ca x Sr 1− x Al 2O 4:Eu 2+ powders show that the structure transforms from monoclinic to hexagonal at x ⩽ 0.5 , and λ p increases from 442.3 to 529.7 nm with decreasing x. For the Ba x Sr 1− x Al 2O 4:Eu 2+ system, the structure transforms from monoclinic to hexagonal at x ⩾ 0.3 , and λ p decreases from 520.5 to 502.2 nm continuously from x = 0 to 1. The shift in λ p 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.