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

Abstract

CaTi4(PO4)6:xEu3+ 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 7F0 → 5H3, 5L7, 5L6, 5D1, 5D2, 5D3, and 5D4 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 5D0 → 7F1, 7F2, 7F3, and 7F4 transitions of Eu3+ ion. The optimal doping concentration of Eu3+ ion is ~ 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 (~ 394 nm) LED chip.