Photoluminescence properties of emission-tunable Ca_8MgLa(PO_4)_7:Eu^2+, Mn^2+ phosphors for white LEDs

Ca8MgLa(PO4)7:Eu2+, Mn2+ phosphors were prepared by solid-state reaction method, and their luminescence properties were studied. The optical bandgap of the Ca8MgLa(PO4)7 host was determined to be about 5.34 eV experimentally. For Eu2+ single-doped samples, broad yellow emission bands were found from 400 to 800 nm, derived from various Eu2+ emission centers in different Ca2+ sites. The corresponding excitation spectra exhibit strong and broad absorption in near ultraviolet region with a red-shift depending on the monitoring wavelengths. For Eu2+-Mn2+ codoped samples, extremely efficient energy transfer from Eu2+ to Mn2+ was found, and tunable emission was realized with the emitting light color ranging from yellow to red. In sum, the investigation results of Ca8MgLa(PO4)7:Eu2+, Mn2+ phosphors indicate their promising applications in white LEDs.