Photoluminescence properties of whitlockite-type Ca9MgK(PO4)7:Eu2+,Mn2+ phosphor

Novel single-phased Eu2+/Mn2+-coactivated whitlockite-type Ca9MgK(PO4)7 phosphors which can emit white light upon UV light excitation, are prepared by the solid-state method, and their luminescence properties are systematically investigated via a combination of X-ray powder diffraction and spectroscopy measurements. For Eu2+-Mn2+ codoped samples, an efficient energy transfer process can takes place and its mechanism is a resonant type via a dipole-quadrupole interaction which can be elucidated by Dexter׳s theoretical model. Following the principle of energy transfer, myriad luminescence colors with a large gamut from blue to purplish red and across white zone in a line in the chromaticity diagram of the CIE can be obtained by simply adjusting the concentration ratio of Eu2+ to Mn2+. Photoluminescence spectra reveal that the white color emission is originated from the combination of two emission bands of Eu2+ and Mn2+ ions. Additionally, their CIE chromaticity coordinates and correlated color temperatures (CCT) have been calculated and discussed in detail. The luminescence suggest that whitlockite-type phosphor, Ca9MgK(PO4)7, co-activated with europium and manganese, is a promising single-phased white-emitting candidate for use in ultraviolet-chip-based white LEDs.