Color-adjustable fluorescence and red persistent luminescence of rare earth-free CaAlSiN3:Mn2+phosphors prepared by combustion synthesis

Increasing interests have been focused on non-rare earth ion of Mn2+-activated nitride phosphors due to their unique luminescent properties. Although rare earth ions (e.g. Eu2+, Ce3+) doped CaAlSiN3 have been extensively studied in phosphor-converted white light emitting diodes (w-LEDs), there have been very few literatures on the fluorescence and persistent luminescence of rare earth-free CaAlSiN3 phosphors. In this work, a series of rare earth-free CaAlSiN3:x Mn2+ (x = 0.05-5%) phosphors have been successfully prepared through the efficient combustion synthesis. With the increase of Mn2+ ions in CaAlSiN3, the adjustment of emission color from yellow to red can be achieved with its transition to be attributed to 4T1 -> 6A1 of Mn2+ at the Al/Si sites (yellow) and Ca sites (red) with diverse occupancy ratios in the CaAlSiN3 host. Moreover, a striking red-color persistent phenomenon originated from the emission of Mn2+ at the Ca sites was observed in these phosphors, among which CaAlSiN3:0.2% Mn2+ showed the best afterglow performance due to its appropriate trap depth of -0.7 eV. We believe that this work is supposed to be an inspiration for exploring novel luminescent materials in rare earthfree nitride material systems.