A novel red-emitting K₂Ca(PO₄)F:Eu²⁺ phosphor with a large Stokes shift

Abstract

We report a KCaPOF:Eu phosphor with a new crystal structure. This phosphor has a large Stokes shift and converts near-ultraviolet light to red luminescence without absorption of other visible light. The mechanism was elucidated by applying a constrained density functional theory to the solved crystal structure.

Site‐Selective Occupancy of Eu2+Toward Blue‐Light‐Excited Red Emission in a Rb3YSi2O7:Eu Phosphor

“…Normally, the energy gap between the 4f ground state and the 5d excited state for free Eu 2+ ions is about 4.2 eV (34 000 cm −1 ) . When the Eu 2+ ions are doped into a given host lattice, the 5d excited state will interact with the coordinating environment, leading to spectroscopic red‐shift as a result of crystal field splitting and centroid shift . For nitride‐based red phosphors, such as CaAlSiN 3 :Eu, Sr 2 Si 5 N 8 :Eu, and Sr[LiAl 3 N 4 ]:Eu, Eu 2+ ions are surrounded by a network of condensed MN 4 tetrahedra (M=Si, Al, Li) and the coordination numbers for the activators are 5, 8, and 8, respectively .…”

Nephelauxetic effect of the hydride ligand in Sr2LiSiO4H as a host material for rare-earth-activated phosphors

“…11 Therefore, to design phosphors with different emitting color requirements, oxides, nitrides, halides, and mixed ligand systems have been used as host materials. 12 Compared to conventional host materials, hydride and hydridebased mixed anion compounds are expected to induce larger centroid shis due to the expansion of electron cloud of the 5d electron. This so-called nephelauxetic effect is generally based on the covalent bonding between cation and anion ligand.…”

Highly Efficient Green‐to‐Yellowish‐Orange Emitting Eu2+‐Doped Pyrophosphate Phosphors with Superior Thermal Quenching Resistance for w‐LEDs

“…Previously, the most reported green/yellowish‐orange Eu 2+ ‐activated phosphors are classified to oxynitride or aluminate . Compared with the above‐mentioned compounds, phosphate has a remarkable advantage in synthesis temperature and cost . However, highly efficient green/yellowish‐orange Eu 2+ ‐activated phosphate phosphors were rarely reported due to a weak nephelauxetic effect of phosphate hosts .…”