Synthesis, luminescence and application of novel europium, cerium and terbium-doped apatite phosphors

Abstract

Novel La₈Ba₂(Si₄P₂O₂₂N₂)O₂:Eu²⁺/Ce³⁺/Tb³⁺ apatite phosphors with tuneable light emission have been successfully synthesized by the conventional solid-state method. The structural and luminescence properties of the newly obtained samples have been studied systematically. The photoluminescence properties show that the Eu²⁺-, Ce³⁺- and Tb³⁺-doped La₈Ba₂(Si₄P₂O₂₂N₂)O₂ samples have strong absorption in the near ultraviolet (n-UV) region. Under n-UV light irradiation, Eu²⁺-doped samples exhibit a narrow bluish green emission band peaking at 496 nm with a full width at half-maximum (FWHM) of 55 nm, which is comparable to the commercial blue emitting BaMgAl₁₀O₁₇:Eu²⁺ (FWHM = 55 nm) phosphor, while La₈Ba₂(Si₄P₂O₂₂N₂)O₂:Ce³⁺,Tb³⁺ presents adjustable emission colour from violet to green by adjusting the concentration of Tb³⁺. The energy-transfer efficiencies and mechanisms have been discussed in detail. The temperature dependent luminescence measurements show that the obtained samples have low thermal quenching. Moreover, a series of white LED devices have been obtained by using the La₈Ba_1.99(Si₄P₂O₂₂N₂)O₂:0.01Eu²⁺/(Sr,Ca)AlSiN₃:Eu²⁺/(Ba,Sr)SiO₄:Eu²⁺/(Sr,Ba,Ca)₁₀(PO₄)Cl₂:Eu²⁺/Sr₂SiO₄:Eu²⁺ phosphor blend. By adding the as-prepared narrow bluish-green-emitting La₈Ba_1.99(Si₄P₂O₂₂N₂)O₂:0.01Eu²⁺ phosphor, the R_a values can increase from 68 to 98, the R9 values increase from 42 to 95, and the corresponding CCT continuously decreases from 6210 to 3086 K, respectively. Our results reveal that the Eu²⁺, Ce³⁺ and Tb³⁺ activated phosphors are promising candidates for WLEDs.