Highly dispersed Eu2+ activated Ca10(PO4)6Cl2 phosphor with enhanced blue emitting through deposition-precipitation process
A series of Eu 2+ activated Ca 10 (PO 4 ) 6 Cl 2 phosphors (ClAp: Eu 2+ ) with enhanced blue emission have been prepared by the deposition precipitation (DP) process. The XRD patterns indicate that Eu 2+ ions are incorporated into Ca 10 (PO 4 ) 6 Cl 2 lattice during the DP process. The ClAp: xEu 2+ -DP phosphor exhibits an super broad excitation band of 250 nm–420 nm consisting of three distinct peaks at 276 nm, 343 nm and 365 nm, ascribed to the 4f 6 → 4f 7 5 d 1 transition of Eu 2+ ions in 4f and 6 h sites. Under 350 nm excitation, ClAp: xEu 2+ -DP phosphors show the intense blue emission at 453 nm and the maximum intensity is obtained when x = 0.3. Notably, an enhanced blue emission intensity of ~2.1 times can be found for ClAp:0.3Eu 2+ -DP phosphor compared with the sample prepared by traditional solid state reaction (SSR) method. Further, the EDX elemental mapping of the phosphor demonstrates that DP process can effectively promote the uniform distribution of Eu 2+ ions on the surface of ClAp crystal and avoid the aggregating problem of activators in SSR method, which can greatly improves the photoluminescence property. It can be concluded from HRTEM images and decay curves that ClAp:0.3Eu 2+ -DP phosphor exhibits characteristic lattice fringes similar to those of ClAp:0.3Eu 2+ -SSR phosphor, but a longer average decay lifetime (392 ns). In addition, the presence of trivalent europium ions on the surface of ClAp: 0.3Eu 2+ -SSR and ClAp: 0.3Eu 2+ -DP phosphors can be identified by XPS analysis . All the results reveal that DP process is an efficient way to prepare highly dispersed Eu 2+ activators in Ca 10 (PO 4 ) 6 Cl 2 host and the ClAp: Eu 2+ -DP phosphors can be the promising candidate for blue emission in white LEDs.
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