A novel single-composition trichromatic white-emitting Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5 : Ce3+/Tb3+/Mn2+ phosphor: synthesis, luminescent properties and applications for white LEDs

A series of single-composition trichromatic white-emitting Sr3.5Y6.5O2(PO4)(1.5)(SiO4)(4.5)(SYPSO) : Ce3+,Tb3+,Mn2+ phosphors were investigated, and the crystal structures and luminescence properties, especially the energy transfer behavior, are discussed in detail. It was found that the SYPSO : Ce3+,Tb3+,Mn2+ phosphors can yield three major RGB emission bands in the visible spectral region: blue emission from the 5d-4f transitions of Ce3+, green emission from the 5(4-)(D)(7)F(J) (J = 3,4,5,6) transitions of Tb3+ and red emission from the T-4(1)((4)G)-(6)A(1)(S-6) transition of Mn2+ ions. The energy transfer process between Ce3+ and Tb3+ and between Ce3+ and Mn2+ have both been demonstrated to be a resonant type via a dipole-dipole mechanism, and the energy transfer (ET) efficiency, as well as the critical distance, have also been estimated. Based on the energy transfer, the emission colors of the obtained phosphors can be tuned from blue to green/red, and eventually to white emission by controlling the doping content of the Tb3+/Mn2+ ions. A white light emitting-diodes (w-LEDs) lamp was finally fabricated using the present phosphor (with the composition of SYPSO : 0.05Ce(3+), 0.25Tb(3+), 0.25Mn(2+)), which exhibited a high color rendering index (R-a) of 89.95 at a correlated color temperature of 6189 K and CIE coordinates of (0.320, 0.318). These results suggested that the present phosphor is a potential single-component white-light phosphor for n-UV-pumped w-LED.