Orange-red-emitting CaTi4(PO4)6:Eu3+ phosphor for white LEDs: synthesis and luminescence properties

CaTi4(PO4)(6):xEu(3+) phosphors are successfully synthesized under air condition by high-temperature solid-state method. The crystal structure, morphology, energy spectrum, atomic percentage, elemental mapping, and luminescence properties are investigated, respectively. Monitored at 594 nm, the excitation spectral bands of CaTi4(PO4)(6):Eu3+ phosphor in the range of 210-550 nm are assigned to the O2--Eu3+ charge transfer band (CTB) and the F-7(0)-> H-5(3), L-5(7), L-5(6), D-5(1), D-5(2), D-5(3), and D-5(4) transitions of Eu3+ ion. With excitation at 394 nm, CaTi4(PO4)(6):Eu3+ phosphor emits orange-red light with the chromaticity coordinates (0.548, 452), and the emission spectral bands in the region from 575 to 720 nm are attributed to the D-5(0)-> F-7(1), F-7(2), F-7(3), and F-7(4) transitions of Eu3+ ion. The optimal doping concentration of Eu3+ ion is similar to 8 mol%. The lifetime of CaTi4(PO4)(6):Eu3+ phosphors decreases from 1.87 to 0.97 ms with increasing Eu3+ concentrations from 1 to 10 mol%. CaTi4(PO4)(6):Eu3+ phosphor has a good thermal stability. The experimental results indicate that CaTi4(PO4)(6):Eu3+ phosphor has an application prospect in white light-emitting diodes (LEDs) based on the near ultraviolet (similar to 394 nm) LED chip.