Effect of sintering temperature on phase transformation and luminescence property of BaAl2Si2O8:Eu2+ phosphor

Abstract

Sintered at different sintering temperatures, Eu2+ doped BaAl2Si2O8 phosphors were synthesised through one-step calcination process of precursors prepared by chemical coprecipitation method. Thermal gravity-differential thermal analysis was used to investigate the initial temperature of phase transition and the optimal sintering temperature of the sample synthesis. The X-ray diffraction patterns confirmed that the sample calcined at 1200°C possessed a single hexagonal phase of BaAl2Si2O8. Although a little BaAl2Si2O8 phase had been produced, BaAl2O4 phase was dominant in the sample calcined at 1000°C. The morphology of the sample observed by scanning electron microscope showed smooth surfaces and nearly spherical shapes at higher sintering temperature. The emission spectrum of the sample calcined at 1000°C was separated into three Gaussians with the maximum at about 455, 501 and 540 nm, due to the 4f7→4f65d transitions of Eu2+ ions occupying the Ba site of BaAl2Si2O8 and the Ba(1) and Ba(2) site of BaAl2O4, respectively. With the increase of sintering temperature, BaAl2Si2O8:Eu2+ phosphor exhibited a blue broad emission band peaking at 455 nm with full width at half maximum about 90 nm under near-ultraviolet excitation at ∼400 nm, and its emission intensity increased considerably due to the improved crystalline and homogeneous distribution of Eu2+ ions.