Fluorescence property of novel near-infrared phosphor Ca2MgWO6:Cr3+

A novel near infrared (NIR) emitting long-lasting phosphorescence (LLP) phosphors of Ca2MgWO6:Cr3+ were prepared by solid-state reaction in air. X-ray diffraction patterns showed that the obtained phosphors have a single-phase monoclinic structure and the incorporation of the dopants did not change the crystal structure. When excited at 371 nm, Ca2MgWO6:Cr3+ phosphors show characteristic broadband NIR fluorescence corresponding to the 4T2→4A2 transitions of Cr3+. The optimal Cr3+ doping concentration is 0.4% (mol). The critical distance between Cr3+ ions has been calculated and the concentration quenching type in Ca2MgWO6:Cr3+ was verified to be a dipole-dipole interaction. The optical spectra and the decay curves of the phosphors indicate that there exists efficient energy transfer from host to Cr3+ ions. The Ca2MgWO6:Cr3+ phosphors also exhibit NIR LLP phenomenon which is seldom presented in non-gallate phosphors. Finally, the possible fluorescence and LLP mechanism and possible energy transfer processes in Ca2MgWO6:Cr3+ phosphor are analyzed with simplified energy level diagrams.