Tailoring cationic configurations in β-Ca3(PO4)2-type matrices for gentle orange emission toward eye-comfort lighting

Rare-earth-doped β-Ca 3 (PO 4 ) 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 Sr 7 LuNaMg 1.5 (PO 4 ) 7 :Eu 2+ was designed based on the crystal structure of Sr 9 Fe 1.5 (PO 4 ) 7 (ICSD No. 93870), whose structure is topologically similar to β-Ca 3 (PO 4 ) 2 . The title phosphor exhibits ultra-broadband emission centered at 599 nm (full-width at half-maximum = 197 nm) under 395 nm n-UV excitation. Structural characterization coupled with spectroscopic studies demonstrates the coexistence of multiple luminescent centers in Sr 7 LuNaMg 1.5 (PO 4 ) 7 :Eu 2+ . A progressive redshift in the emission color coordinates was observed with increasing Eu 2+ 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 Sr 7 LuNaMg 1.5 (PO 4 ) 7 :Eu 2+ phosphor for high-performance white light-emitting diodes, demonstrating it as a competitive luminescent material for advanced lighting technologies.