Effect of anionic group [SiO4]4−/[PO4]3− on the luminescence properties of Dy3+-doped tungstate structural compounds

Abstract

Novel scheelite structures of Li2Ca(WO4)2, Li2Ca2(WO4)(SiO4), and LiCa2(WO4)(PO4) fluorescent materials were successfully prepared using a high-temperature solid-phase process. The compounds were characterized by X-ray diffraction and energy dispersive spectroscopy. The tests revealed that the substitution of [WO4]2− by [SiO4]4− or [PO4]3− tetrahedron in tungstate had no significant influence on the crystal structure of the Li2Ca(WO4)2. When Dy3+ ions were introduced as an activator at an optimum doping concentration of 0.08 mol%, all of the as-prepared phosphors generated yellow light emissions, and the emission peak was located close to 576 nm. Replacing [WO4]2− with [SiO4]4− or [PO4]3− tetrahedron significantly increased the luminescence of the Li2Ca(WO4)2 phosphors. Among them, the LiCa2(WO4)(PO4):0.08Dy3+ phosphor had the best luminescence properties, decay life (τ = 0.049 ms), and thermal stability (87.8%). In addition, the as-prepared yellow Li2Ca(WO4)2:0.08Dy3+, Li2Ca2(WO4)(SiO4):0.08Dy3+, and LiCa2(WO4)(PO4):0.08Dy3+ phosphor can be used to fabricate white light emitting diode (LED) devices.

Spectral studies of thermally stable Dy3+/Sm3+ co-doped Li2Ba5W3O15 phosphors for warm white LEDs

“…Notably, elements with low energy, like Li, show no peaks in their EDX spectra, which is consistent with observations found in the literature [33]. [34], however, the transitions corresponding to 6 F 3/2 , 6 F 5/2 and 6 F 7/2 excited states from the ground state 6 H 15/2 are represented by the remaining peaks at 736, 792 and 888 nm, were related to Dy 3+ ions [35,36].…”

“…The peaks corresponding to 472, 946, 1072, 1272, 1378, 1474 and 1530 nm wavelength shows the transition from the ground state, i.e. 6 H 5/2 to various excited states 4 I 11/2 , 6 F 11/2 , 6 F 9/2 , 6 F 7/2 , 6 F 5/2 , 6 H 13/2 and 6 H 11/2 , related to Sm 3+ ions[34], however, the transitions corresponding to 6 F 3/2 , 6 F 5/2 and 6 F 7/2 excited states from the ground state 6 H 15/2 are represented by the remaining peaks at 736, 792 and 888 nm, were related to Dy 3+ ions[35,36].The optical absorption near the band edge is represented by the Kubelka-Munk (K-M) function, which can be utilized to address the band gap energy (E g )[37]:…”

Metal–Organic-Framework-Derived Ball-Flower-like Porous Co3O4/Fe2O3 Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Activity

“…(ii) The p-n heterojunction that formed between Fe 2 O 3 and Co 3 O 4 could promote the separation of photo-generated electron and hole pairs [27][28][29][30]. The promoted charge separation, and thus the inhibited charge recombination, was witnessed by the significantly decreased photoluminescence (PL) intensity of CF composites compared to pristine Fe 2 O 3 particles, as displayed in Figure S5 of the Supplementary Materials [31][32][33][34][35][36][37][38]. The variation in the RhB degradation efficiency of CF in different pH conditions is presented in Figure 3b, suggesting that the catalyst could maintain a superior photocatalytic degradation activity in the pH range of 4-10, despite the fact that the degradation rate decreased to a certain extent in a strong acid environment (pH ≤ 2).…”

Emission Enhancement of Eu3+ Ions in LiY(PO3)4 Phosphate Phosphors via Anionic SO4 2− Substitution

“…Structural substitution is an easy method of increasing the luminescence intensity. Partial substitution of anion groups in structure with crystal field change and charge compensation can enhance the luminescence performance of phosphors, and there are many reports about the improvement of luminescence properties of phosphors via anionic substitution such as Ca 9.75 Eu 0.5 (VO 4 ) 7 , 33 Y 2 (MoO 4 ) 3 :Sm 3+ , 34 NaLa(MoO 4 ) 2 :Eu 3+ , 35 Ca 19 Zn 2 (PO 4 ) 14 :Dy 3+ , 36 Na 2 Y(MoO 4 )(PO 4 ):Tb 3+ ,Eu 3+ , 37 Li 2 Ca(WO 4 ) 2 : Dy 3+ , 38 LaNa (MoO 4 ) 2 :Dy 3+ , 39 and CaMoO 4 :Eu 3+ . 40 In the present work, red emitting Eu 3+ -doped LiY(PO 3 ) 4(1−x) (SO 4 ) 4x phosphate phosphors are synthesized by a traditional solid state reaction method.…”