Tailoring Cationic Configurations in Β-Ca3(Po4)2-Type Matrices for Gentle Orange Emission Toward Eye-Comfort Lighting

Abstract

Rare-earth-doped β-Ca3(PO4)2-type derivatives are a research hotspot in optoelectronics materials, yet achieving eye-friendly comfortable emission in such multication lattice systems remains a challenge. Herein, a novel orange-emitting phosphor Sr7LuNaMg1.5(PO4)7:Eu2+ was designed based on the crystal structure of Sr9Fe1.5(PO4)7 (ICSD No. 93870), whose structure is topologically similar to β-Ca3(PO4)2. The title phosphor exhibits ultra-broadband emission centered at 599 nm (FWHM ≈ 197 nm) under 395 nm n-UV excitation. Structural characterization coupled with spectroscopic studies demonstrates the coexistence of multiple luminescent centers in Sr7LuNaMg1.5(PO4)7:Eu2+. A progressive redshift in the emission color coordinates was observed with increasing Eu2+ doping concentrations, attributable to selective cation occupancy and crystal field effects. The concentration-dependent quenching mechanism was elucidated through comprehensive analysis based on Dexter's theory. Characterization of quantum efficiency, thermal stability, and packing density validated the suitability of Sr7LuNaMg1.5(PO4)7:Eu2+ phosphor for high-performance white light-emitting diodes, demonstrating it as a competitive luminescent material for advanced lighting technologies.

Keywords: Orange-emitting phosphor, Sr7LuNaMg1.5(PO4)7:Eu2+, β-Ca3(PO4)2-type, WLEDs