The role of europium and dysprosium in the bluish-green long lasting Sr_2Al_2SiO_7:Eu~(2+), Dy~(3+) phosphor by solid state reaction method

摘要

The Sr_2Al_2SiO_7; Sr_2Al_2SiO_7:Eu~(2+); Sr_2Al_2 SiO_7:Dy~(3+) and Sr_2Al_2SiO_7:Eu~(2+), Dy~(3+) phosphors were synthesized by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, thermoluminescence (TL), photolu-minescence (PL) long afterglow and mechanoluminescence (ML) techniques. The crystal structures of sintered phosphors were gehlenite type structure which belongs to the tetragonal crystallography. The TL properties of these phosphors were investigated and results were also compared. Under the ultraviolet excitation, the emission spectra of Sr_2Al_2SiO_7:Eu~(2+) and Sr_2Al_2SiO_7:Eu~(2+), Dy~(3+) phosphors were composed of a broad band peaking at 490 nm (bluish-green), belonging to the broad emission band and Sr_2Al_2 SiO_7:Dy~(3+) phosphor emits the white light, which was confirmed from the calculated CIE coordinates. When the Sr_2Al_2SiO_7:Eu~(2+) phosphor is co-doped with Dy~(3+), the intensity of TL, PL, afterglow and ML is strongly enhanced. Decay graph indicate that both the sintered phosphors contains fast decay and slow decay process. The ML intensities of Sr_2Al_2SiO_7:Dy~(3+); Sr_2Al_2SiO_7:Eu~(2+) and Sr_2Al_2SiO_7:Eu~(2+), Dy~(3+) phosphors were proportionally increased with the increasing impact velocity of the moving piston, which suggests that these phosphor can be used as sensors to detect the stress of an object.