Effect of Dy on properties of red long-afterglow phosphor Sr3Al2O6:Eu2+,Dy3+

The red long afterglow phosphor Sr3Al2O6:Eu2+,Dy3+ was prepared by sol-gel method. The crystal structure was characterized by X-ray diffraction. The results reveal that the samples are composed of single Sr3Al26 phase at 1200℃, and the small amount of doped rare earth ions Eu2 and Dy3 has no effect on the Sr3Al26 phase composition. The excitation, emission and afterglow spectra were investigated by fluorescence spectrophotometer technique. The broad excitation spectra in the range of 400—550 nm were found in the Sr3Al26:Eu2 and Sr3Al26:Eu2,Dy3 phosphors. The broad band spectrum is associated with defects and vacancies of host material and the peak at 530.1 nm can be assigned to the recombination of donor-acceptor pairs of y·Sr-V″Sr from dysprosium doping in the Sr3Al2O6. With the increasing concentration of Dy below 0.03, the emission intensity of Sr3-002-yAl26:0.02Eu2,yDy3 phosphors increases, and the samples exhibit the red light emission spectra with the main emission peak at 612 nm under an excitation of 473 nm. The red emission has a broad-band feature, belonging to the emission of the 4f65d1→4f7 of Eu2ions. With the increasing concentration of Dy within the range of 0.03—0.06, there was a new emission peak in the green region, and the emission intensities of the two peaks at 530 nm and 612 nm decrease. The afterglow time of the Sr295Al26:0.02Eu2,0.03Dy3 phosphors lasts 540s≥1　mcd/m2 after removal of excitation. The Dy3 ions are auxiliary activator in the Sr3Al2O6:Eu2+,Dy3+ phosphors.