The role of europium and dysprosium in the bluish-green long lasting Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ phosphor by solid state reaction method

Abstract

The Sr₂Al₂SiO₇; Sr₂Al₂SiO₇:Eu²⁺; Sr₂Al₂SiO₇:Dy³⁺ and Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ 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), photoluminescence (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 Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ phosphors were composed of a broad band peaking at 490 nm (bluish-green), belonging to the broad emission band and Sr₂Al₂SiO₇:Dy³⁺ phosphor emits the white light, which was confirmed from the calculated CIE coordinates. When the Sr₂Al₂SiO₇:Eu²⁺ phosphor is co-doped with Dy³⁺, 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 Sr₂Al₂SiO₇:Dy³⁺; Sr₂Al₂SiO₇:Eu²⁺ and Sr₂Al₂SiO₇:Eu²⁺, Dy³⁺ 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.