Photoluminescence Optimization of Ca3(PO4)2:Eu3+ Phosphors By Crystallinity Improvement And Charge Compensation

Abstract

In this study, in order to improve the photoluminescence properties of Ca3(PO4)2:Eu3+ phosphors, alkali metal ions (Li+, Na+, and K+) were doped into the Ca2.91(PO4)2:Eu3+ phosphors, and the effects of alkali metal ions on the structural and optical properties were investigated. The alkali metal ions significantly enhanced the emission intensity and improved the emission color quality because they induced the charge balance, improved the crystalline quality, and stabilized the crystal structure, namely, the alkali metal ions in Ca3(PO4)2:Tb3+ acted as both charge compensators and fluxes. Of the alkali metal ions used, Li+ was an optimal cation to improve the emission intensity and color purity. The Ca2.82(PO4)2:0.09Eu3+, 0.09Li+ phosphor showed a 40% stronger red emission intensity than that of the Ca2.91(PO4)2:0.09Eu3+ phosphor. We demonstrate that incorporating alkali metal ions, especially Li+, is important to improve the emission intensity and color purity.

Europium-Doped Calcium Silicate Nanoparticles as High-Quantum-Yield Red-Emitting Phosphors

“…Unlike the 5 D 0 → 7 F 1 (591 nm) transition insensitive to site symmetry and surroundings, the 5 D 0 → 7 F 2 (614 nm) and 5 D 0 → 7 F 4 (712 nm) transitions have a hypersensitive electric dipole nature to be affected by the site symmetry. For the Ca 2–0.05 SiO 4 : 0.05 Eu 3+ samples, when the Eu 3+ (0.095 nm) ions enter into the host lattice and replace the Ca 2+ (0.099 nm) ions, vacancies (VCa) are formed owing to the valence differences between Eu 3+ and Ca 2+ . Therefore, the site symmetry is reduced and the delocalization of the Eu 3+ ions occurs in a distorted (or symmetric) cationic environment, which allows the forbidden transition in Ca 2–0.05 SiO 4 : 0.05 Eu 3+ .…”