Spray pyrolysis synthesis of MAl₂O₄:Eu² (M=Ba, Sr) phosphor for UV LED excitation

The UV excited green emitting Eu²-activated BaAl ₂O₄ and SrAl₂O₄ phosphors were prepared by ultrasonic spray pyrolysis at low temperature. The morphologies of phosphors were spherical and ∼1 μm size with non-aggregation. The BaAl₂O₄:Eu² and SrAl₂O ₄:Eu² were efficiently excited under UV range from 320 to 370 nm, and exhibited broad band emission at about 500 and 520 nm, respectively, corresponding to the 5d4f transition of Eu². The detailed properties of crystal structure and luminescence behaviors were discussed by measurements of X-ray diffraction and photoluminescence. Phosphor conversion LEDs were fabricated by combining GaN-based 380 nm emitting UV LED as an optical pumping source with the prepared phosphors. The BaAl₂O₄:Eu ² phosphor LEDs showed the CIE coordinate of (0.171, 0.432) in bluish-green emission, and SrAl₂O₄:Eu² phosphor LEDs showed that of (0.224, 0.518) in green emission.