Effect of B2O3 content on Eu3+−Surrounding in the system SrO−x.B2O3 containing Eu3+ ions prepared by combustion method

NaGdF4:Eu3+ nanocrystalline: an in-depth study of energy transfer processes and Judd–Ofelt analysis using the luminescence excitation spectrum

“…The variation in the R ratio is insignificant when changing the Eu 3+ concentration. In addition, the R ratio in NaGdF 4 :Eu 3+ nanocrystalline matrices is equivalent to that in some nanocrystalline matrices, such as LaPO 4 :Eu 3+ (1.40), 19 LaAlO 3 :Eu 3+ (1.25), 26 and β-NaGdF 4 :Eu 3+ (1.60), 6 but is lower than that in β-NaGdF 4 :Eu 3+ (2.69), 24 Sr 2 B 2 O 5 :Eu 3+ (2.53), 27 and SrB 2 O 4 :Eu 3+ (3.74). 27 The small value of the R ratio in our case implies that the Eu 3+ ions occur at the high symmetry sites in the NaGdF 4 lattice.…”

“…In addition, the R ratio in NaGdF 4 :Eu 3+ nanocrystalline matrices is equivalent to that in some nanocrystalline matrices, such as LaPO 4 :Eu 3+ (1.40), 19 LaAlO 3 :Eu 3+ (1.25), 26 and β-NaGdF 4 :Eu 3+ (1.60), 6 but is lower than that in β-NaGdF 4 :Eu 3+ (2.69), 24 Sr 2 B 2 O 5 :Eu 3+ (2.53), 27 and SrB 2 O 4 :Eu 3+ (3.74). 27 The small value of the R ratio in our case implies that the Eu 3+ ions occur at the high symmetry sites in the NaGdF 4 lattice. Another feature of the 5 D 0 → 7 F 1 luminescence band is that its structure depends on the symmetric group of crystals at the site Eu 3+ ion.…”

“…In the host matrices with high energy phonon, these luminescence bands are very weak or cannot be observed even at low concentrations of Eu 3+ . 26–30 As depicted in Fig. 6 and 4b, for the low Eu 3+ concentration ( e.g.…”

“…25 In addition, a weak emission band in the range of 645–670 nm, which is produced by the 5 D 0 → 7 F 3 transition, is observed in the spectra. For the Eu 3+ ions, the 5 D 0 → 7 F 0 transition, which generates an emission line at around 578 nm, is observed apparently in some host matrices, such as the LaAlO 3 :Eu 3+ nanophosphors, 26 LaPO 4 :Eu 3+ nanoparticles, 9 SrB 2 O 4 :Eu 3+ phosphor 27 as well as the lead fluoroborate 28 and potassium-aluminoborotellurite 29 glasses. In the case of the prepared NaGdF 4 :Eu 3+ nanocrystalline, by zooming the emission 577–580 nm region, the 5 D 0 → 7 F 0 band is also observed for all samples (see inset in Fig.…”

“…In addition, the Ω 2 and R parameters of the NaGdF 4 :Eu 3+ nanocrystalline are much smaller than those in some oxide compounds. 9,26,27,30 The smaller values of R and Ω 2 indicate a lower degree of ligand asymmetry as well as the covalence of the Eu 3+ –ligand bond in β-NaGdF 4 :Eu 3+ nanocrystalline compared to those in some oxide nanocrystalline materials. The decrease in the Ω 2 parameter of RE 3+ ions in fluoride compounds compared with that in oxide materials seems to be closely related to the electronegativity of ligand anions.…”