Phase transition and multicolor luminescence of Eu2+/Mn2+-activated Ca3(PO4)2 phosphors

• A series of novel Eu2+: Ca3(PO4)2 phosphors were successfully synthesized.
• Phase transition of Ca3(PO4)2 from orthorhombic to rhombohedral occurred when Mn2+ ions were doped.
• The phosphors exhibited tunable multi-color luminescence.
• The quantum yield of 0.05Eu2+: Ca2.95(PO4)2 phosphor can reach 56.7%.
• The analyses of phosphors were carried out by many measurements.

Intense blue-green-emitting Eu2+: Ca3(PO4)2 and tunable multicolor-emitting Eu2+/Mn2+: Ca3(PO4)2 phosphors are prepared via a solid-state reaction route. Eu2+-doped orthorhombic Ca3(PO4)2 phosphor exhibits a broad emission band in the wavelength range of 400–700 nm with a maximum quantum yield of 56.7%, and the emission peak red-shifts gradually from 479 to 520 nm with increase of Eu2+ doping content. Broad excitation spectrum (250–420 nm) of Eu2+: Ca3(PO4)2 matches well with the near-ultraviolet LED chip, indicating its potential applications as tri-color phosphors in white LEDs. Interestingly, Mn2+ co-doping into Eu2+: Ca3(PO4)2 leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu2+ → Mn2+ energy transfer, under 365 nm UV lamp excitation.

We have synthesized Eu2+ doped and Eu2+/Mn2+ co-doped Ca3(PO4)2 phosphors. The emitting color varies from blue to green with increasing of Eu2+ content for the Eu2+-doped phosphor, and the quantum yield of the 0.05Eu2+: Ca2.95(PO4)2 sample reaches 56.7%. Interestingly, Mn2+ co-doping into Eu2+: Ca3(PO4)2 leads to its phase transition from orthorhombic to rhombohedral, and subsequently generates tunable multi-color luminescence from green to red via Eu2+ → Mn2+ energy transfer.Figure optionsDownload as PowerPoint slide