Structure and luminescence behavior of a single-ion activated single-phased Ba2Y3(SiO4)3F:Eu white-light phosphor

Abstract

The development of a single-ion activated single-phased white-light phosphor is of great importance in the field of near ultraviolet based w-LED lighting. In this work, a Ba₂Y₃(SiO₄)₃F:Eu fluoride apatite, which shows a broad emission band covering the entire visible region with tunable color rendition, was successfully synthesized via a high-temperature solid-state route. The microstructure and composition of the phosphor were carefully examined with the aid of XRD Rietveld refinement, HRTEM and SEM analyses, as well as XPS measurement. Spectroscopic studies revealed the site occupancy conditions of Eu²⁺, i.e., the Eu²⁺(I) band centering at 470 nm originates from the [BaO₉] 4f site, while the Eu²⁺(II) one peaking at 600 nm comes from the [BaO₆F] 6h site. Interestingly, the obtained white light can be readily tuned from cool to warm just by varying the Eu doping content. The brightest luminescence was achieved when the Eu concentration reached 1 mol%, beyond which the d–d interaction-based energy transfer between Eu²⁺ ions would result in concentration quenching. The underlying mechanism of the incomplete conversion from Eu³⁺ to Eu²⁺ under a reducing atmosphere was explored, which was believed to be caused by the rigid framework of the crystal structure. After coupling Ba₂Y₃(SiO₄)₃F:Eu with a commercial 3W 370 nm UV chip, the constructed w-LED yielded warm white light with a CIE coordinate of (0.402, 0.371), CCT of 3530 K, and CRI of 83.5, upon being driven by a 350 mA forward-biased current.