Crystal-Site Engineering of Novel Na3KMg7(PO4)6–x(BO3)x:Eu2+ Phosphors for Full-Spectrum Lighting

The "cyan gap" is the bottleneck problem in violet-driven full-spectrum white-light-emitting diodes (wLEDs) in healthy lighting. Accordingly, we develop a novel broadband-blue-cyan emission Na₃KMg₇(PO₄)_6-x(BO₃)_x:Eu²⁺ (NKMPB:Eu²⁺) phosphor via crystal-site engineering. This phosphor is derived from the Na₃KMg₇(PO₄)₆:Eu²⁺ phosphor, which shows desired abundant cyan emissive components. A comparative study is conducted to reveal the microstructure-property relationship and the key influential factors to its spectrum distribution. It can be found that the introduced (BO₃)^3- units can manipulate the site-selective occupation of Eu²⁺ activators, asymmetrically broadening the emission spectrum in NKMPB:Eu²⁺. Considering detailed luminescence performance analysis and the density functional theory calculations, a new substitution pathway of Eu²⁺ is created by substituting (PO₄)^3- with (BO₃)^3- units, making partial Eu²⁺ ions enter the Mg²⁺ (CN = 5, CN = 6) crystallographic sites, and yielding an extra emission band at 600 nm (16667 cm^-1) and especially 501 nm (19960 cm^-1). Meanwhile, a high-color-quality full-spectrum-emitting wLEDs was fabricated, upon 100 mA forward-bias current driven. Due to the achieved extra cyan emissive components of NKMPB:Eu²⁺, the constructed NKMPB:Eu²⁺-based wLEDs show better color rendering ability (∼90.9) than that of Na₃KMg₇(PO₄)₆:Eu²⁺-based wLEDs (∼86.3), and also demonstrate its great potential in full-spectrum healthy lighting.