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

Abstract

A series of single-doped Ca₉Y(PO₄)₅(SiO₄)F_1.5O_0.25:Ln³⁺ (Ln³⁺ = 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)F_1.5O_0.25:Eu³⁺/Tb³⁺/Dy³⁺/Sm³⁺ phosphors show the characteristic emissions of Eu³⁺ (⁵D₀–⁷F₂, red), Tb³⁺ (⁵D₄–⁷F₅, green), Sm³⁺ (⁴G_5/2–⁶H_7/2, red), and Dy³⁺ (⁴F_9/2–⁶H_13/2, yellow). The emission intensities of Ca₉Y_(1−x/z)(PO₄)₅(SiO₄)F_1.5O_0.25:xEu³⁺/zSm³⁺ 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)F_1.5O_0.25: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)F_1.5O_0.25:Eu³⁺/Sm³⁺) and exhibited a red emission with high color purity. All the results indicate that Ca₉Y(PO₄)₅(SiO₄)F_1.5O_0.25:Ln³⁺ phosphors are promising phosphors for white LEDs.