Effect of Zn deficiency on the enhancement of yellowish green persistent phosphor Dy3+-activated SrZn2(PO4)(2)

The yellowish green long persistent phosphors SrZn2-delta-x(PO4-0.5 delta)(2):xDy(3+) were prepared using high temperature solid state method with decay time of about 6 h. The material shows the strongest yellow emission peak at 572 nm attributed to the F-4(9/2) -> H-4(13/2) transition of Dy3+, as well as the second strongest blue one at 482 nm which is contributed by the transitions F-4(9/2) -> H-4(15/2) of Dy3+ and the Zn defects. The compounds of XPS, TL, and EPR spectra as well as the defect equation were used to analyze various defects in the materials. Dy3+ ions are acted as both emission centers and defect suppliers, and Zn deficiency is beneficial to the improvement of luminescence properties of SrZn2-delta-x(PO4-0.53)(2): xDy(3+). Based on the energy band theory and the crystal defect theory, the luminescence mechanism of materials was explored.