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-x2yMg0.7K1+ (y)(PO4)(7):0.07Eu(2+), xMn(2+), yTb(3+) (CMKP:0.07Eu(2+), xMn(2+), yTb(3+), 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:0.07Eu(2+) phosphor shows an asymmetric bluish-green emission band with a dominant peak at 460 nm. By introducing Tb3+ and Mn2+ into the CMKP:0.07Eu(2+) 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:0.07Eu(2+), 0.05Mn(2+), 0.3Tb(3+) sample. The excitation spectra cover a wide wavelength region from 240 to 450 nm, which could well match the emission wavelength of a nearultraviolet 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:0.07Eu(2+), xMn(2+), yTb(3+) phosphors could apply to white LEDs.