Syntheses, crystal structures and photoluminescence properties of Ca9Y(PO4)5(SiO4)F1.5O0.25:Ln3+ (Ln3+ = Eu3+/Tb3+/Dy3+/Sm3+) phosphors for near-UV white LEDs

A series of single-doped Ca9Y(PO4)(5)(SiO4)F1.5O0.25:Ln(3+) (Ln(3+) = Eu3+/Tb3+/Dy3+/Sm3+) phosphors have been prepared via conventional high-temperature solid-state reaction. The structural refinement, photoluminescence properties, and decay curves were studied in detail. Under near-UV excitation, the Ca9Y(PO4)(5)(SiO4)F1.5O0.25:Eu3+/Tb3+/Dy3+/Sm3+ phosphors show the characteristic emissions of Eu3+ (D-5(0)-F-7(2), red), Tb3+ (D-5(4)-F-7(5), green), Sm3+ ((4)G(5/2)-H-6(7/2), red), and Dy3+ (F-4(9/2)-H-6(13/2), yellow). The emission intensities of Ca9Y(1-x/z)(PO4)(5)(SiO4)F1.5O0.25:xEu(3+)/zSm(3+) are maximized when x = 0.16 and z = 0.10, and the concentration quenching mechanisms are both dominated by dipole-dipole interactions. The excitation spectra of the Ca9Y(PO4)(5)(SiO4)F1.5O0.25:Eu3+/Sm3+ phosphors show the strongest absorption at about 400 nm, which matches well with the commercially available near-UV-emitting InGaN-based light emitting-diode (LED) chip. Finally, a red LED was fabricated using the present phosphors (with the composition of Ca9Y(PO4)(5)(SiO4)F1.5O0.25:Eu3+/Sm3+) and exhibited a red emission with high color purity. All the results indicate that Ca9Y(PO4)(5)(SiO4)F1.5O0.25:Ln(3+) phosphors are promising phosphors for white LEDs.