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 Sr3Al2O6 phase at 1200 degrees C, and the small amount of doped rare earth ions (Eu2+ and Dy3+) has no effect on the Sr3Al2O6 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 Sr3Al2O6 : Eu2+ and Sr3Al2O6 : 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 Dy-Sr-V"(Sr) from dysprosium doping in the Sr3Al2O6. With the increasing concentration of Dy below 0.03, the emission intensity of Sr3-0.02-gamma Al2O6 : 0.02Eu(2+), yDy(3+) 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 4P(6)5d(1)-> 4f(7) of Eu2+ ions. With the increasing concentration of Dy within the r-ange 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 Sr2.95Al2O6 : 0.02Eu(2+), 0.03 Dy3+ phosphors lasts 540 s(>= 1 mcd/m(2)) after removal of excitation. The Dy3+ ions are auxiliary activator in the Sr3Al2O6 : Eu2+, Dy3+ phosphors.