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

Abstract

A series of single-composition trichromatic white-emitting Sr_3.5Y_6.5O₂(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 ⁵D₄–⁷F_J (J = 3, 4, 5, 6) transitions of Tb³⁺ and red emission from the ⁴T₁(⁴G)–⁶A₁(⁶S) 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 : 0.05Ce³⁺, 0.25Tb³⁺, 0.25Mn²⁺), 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.