Discovery of New Solid Solution Phosphors via Cation Substitution-Dependent Phase Transition in M₃(PO₄)₂:Eu²⁺ (M = Ca/Sr/Ba) Quasi-Binary Sets

Abstract

The cation substitution-dependent phase transition was used as a strategy to discover new solid solution phosphors and to efficiently tune the luminescence property of divalent europium (Eu2+) in the M3(PO4)2:Eu2+ (M = Ca/Sr/Ba) quasi-binary sets. Several new phosphors including the greenish-white SrCa2(PO4)2:Eu2+, the yellow Sr2Ca(PO4)2:Eu2+, and the cyan Ba2Ca(PO4)2:Eu2+ were reported, and the drastic red shift of the emission toward the phase transition point was discussed. Different behavior of luminescence evolution in response to structural variation was verified among the three M3(PO4)2:Eu2+ joins. Sr3(PO4)2 and Ba3(PO4)2 form a continuous isostructural solid solution set in which Eu2+ exhibits a similar symmetric narrow-band blue emission centered at 416 nm, whereas Sr2+ substituting Ca2+ in Ca3(PO4)2 induces a composition-dependent phase transition and the peaking emission gets red shifted to 527 nm approaching the phase transition point. In the Ca3–x Ba x (PO4)2:Eu2+ set, the validity of crystallochemical design of phosphor between the phase transition boundary was further verified. This cation substitution strategy may assist in developing new phosphors with controllably tuned optical properties based on the phase transition.

Deep red emission in Eu2+-activated Sr4(PO4)2O phosphors for blue-pumped white LEDs

“…23 Another interesting model for large red shifts has been discussed regarding the distortion in Ca 3Àx Sr x (PO 4 ) 2 :Eu 2+ . 24 Sr 2 Ca(PO 4 ) 2 :Eu 2+ has a lattice volume of 3843 Å 3 and exhibits an emission peak wavelength at 527 nm, while b-Ca 3 (PO 4 ) 2 :Eu 2+ with a smaller unit cell volume of 3533 Å showed a shorter emission peak wavelength at 416 nm. In their discussions, larger neighbouring-cations decrease Eu-O bond lengths as a result of higher stress when larger cations replaced smaller ions.…”

New Y2BaAl4SiO12:Ce3+ yellow microcrystal-glass powder phosphor with high thermal emission stability

“…Intending to develop a new yellow candidate with less rare earth element usage than YAG:Ce, in this paper, we report the Y 2 BaAl 4 SiO 12 :Ce composition artificially created from YAG:Ce by using the solid state design, [15][16][17] where a YO 8 polyhedron is…”

Near UV-pumped yellow-emitting Sr9MgLi(PO4)7:Eu2+ phosphor for white-light LEDs

“…Among them, β-Ca 3 (PO 4 ) 2 -type compounds have prompted remarkable attention as phosphor host materials because of their versatile structural types and abundant occupation sites for activators [13,14]. There are five independent cationic crystallographic sites in β-Ca 3 (PO 4 ) 2 host and the coordination number is as follows: Ca(1) is 7-coordinated, Ca(2) and Ca(3) is 8-coordinated, Ca(4) is 3-coordinated, and Ca(5) is 6-coordinated [15].…”