White-light emission in a single-phase Ca9.3Mg0.7K(PO4)7:Eu2+,Tb3+,Mn2+ phosphor for light-emitting diodes

To explore new white-emitting phosphor material for LEDs, a series of Ca9.23−x-2yMg0.7K1+y(PO4)7:0.07Eu2+,xMn2+,yTb3+ (CMKP:0.07Eu2+,xMn2+,yTb3+, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 1.0) phosphors were prepared using the solid-state reaction method, and their photoluminescence properties were studied. Upon 365-nm excitation, the CMKP:0.07Eu2+ phosphor shows an asymmetric bluish-green emission band with a dominant peak at 460 nm. By introducing Tb3+ and Mn2+ into the CMKP:0.07Eu2+ phosphor, white emission can be obtained, whose chromaticity coordinates and correlated color temperature are (0.366, 0.362) and 4306 K, respectively, for the CMKP:0.07Eu2+,0.05Mn2+,0.3Tb3+ sample. The excitation spectra cover a wide wavelength region from 240 to 450 nm, which could well match the emission wavelength of a near-ultraviolet LED chip. In Eu2+-Tb3+-Mn2+ tri-doped CMKP, three energy-transfer (ET) types have been found, i.e., Eu2+→Tb3+, Eu2+→Mn2+, and Tb3+→Mn2+. The corresponding ET processes and mechanism are discussed. The results of the above investigation imply that the CMKP:0.07Eu2+,xMn2+,yTb3+ phosphors could apply to white LEDs.