Tunable luminescence properties and energy transfer of single-phase Ca4(PO4)2O: Dy3+, Eu2+ multi-color phosphors for warm white light
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The novel Ca4−x(PO4)2O: xDy3+ and Ca4−x−y(PO4)2O: xDy3+, yEu2+ multi-color phosphors were synthesized by traditional solid-state reaction. The crystal structure, particle morphology, photoluminescence properties and energy transfer process were investigated in detail. The X-ray diffraction (XRD) results demonstrate that the products showed pure monoclinic phase of Ca4(PO4)2O when x < 0.1. The scanning electron microscopy (SEM) indicated that the phosphors were grain-like morphologies with diameters of ~ 3.7–7.0 μm. Under excitation of 345 nm, Dy3+-doped Ca4(PO4)2O phosphors showed multi-color emission bands at 410, 481 and 580 nm originated from oxygen vacancies and Dy3+. Interestingly, Ca4(PO4)2O: Dy3+, Eu2+ phosphors exhibited blue emission band at 481 nm and broad emission band from 530 to 670 nm covering green to red regions. The energy transfer process from Dy3+ to Eu2+ was observed for the co-doped samples, and the energy transfer efficiency reached to 60% when Eu2+ molar concentration was 8%. In particular, warm/cool/day white light with adjustable CCT (2800–6700 K) and high CRI (Ra > 85) can be obtained by changing the Eu2+ co-doping contents in Ca4(PO4)2O: Dy3+, Eu2+ phosphors. The optimized Ca3.952(PO4)2O: 0.04Dy3+, 0.008Eu2+ phosphor can achieve the typical white light with CCT of 4735 K and CRI of 87.
This research is financially supported by the Natural Science Foundation of Liaoning Province (20170540065), the General Project of Liaoning Provincial Education Department (2016J057) and the Start-up Funding for Doctoral researchers of Dalian Polytechnic University (61020726).
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