Color-Tunable and white luminescence properties via energy transfer in single-phase KNaCa_2(PO_4)_2:A (A = Ce ~(3+), Eu~(2+), Tb~(3+), Mn~(2+), Sm ~(3+)) phosphors

摘要

A series of single-phase phosphors based on KNaCa_2(PO _4)_2 (KNCP):A (A = Ce~(3+), Eu~(2+), Tb~(3+), Mn~(2+), Sm~(3+)) have been prepared via the Pechini-type sol-gel method. Photoluminescence (PL) and cathodoluminescence (CL) properties of Ce~(3+)-, Eu~(2+)-, Tb~(3+)-, Mn ~(2+)-, and Sm~(3+)-activated KNCP phosphors were investigated. For the A singly doped KNCP samples, they exhibit the characteristic emissions of the A activator. Na+ ions exhibit the best charge compensation result among Li+, Na+, and K+ ions for Ce ~(3+)-, Tb~(3+)-, and Sm~(3+)-doped KNCP samples. The energy transfers from Ce~(3+) to Tb~(3+) and Mn~(2+) ions as well as Eu~(2+) to Tb~(3+) and Mn~(2+) have been validated. The emission colors of KNCP:Ce~(3+)/Eu~(2+), Tb ~(3+)/Mn~(2+), Na+ samples can be adjusted by energy transfer process and changing the Tb~(3+)/Mn~(2+) concentration. More importantly, white light emission in KNCP:Eu~(2+), Mn~(2+) system has been obtained. The KNCP:Tb~(3+), Na+ sample shows tunable luminescence from blue to cyan and then to green with the change of Tb~(3+) concentration due to the cross-relaxation from ~5D_3 to ~5D_4. A white emission can also be realized in the single-phase KNCP host by reasonably adjusting the doping concentrations of Tb~(3+) and Sm~(3+) (reddish-orange emission) under low-voltage electron beam excitation. Additionally, the temperature-dependent PL properties of as-prepared phosphors reveal that the KNCP host has good thermal stability. Therefore, the KNCP:A (A = Ce ~(3+), Eu~(2+), Tb~(3+), Mn~(2+), Sm ~(3+)) phosphors could be regarded as good candidates for UV W-LEDs and FEDs.