Site Occupancy and VUV–UV–Vis Photoluminescence of the Lanthanide Ions in BaY₂Si₃O₁₀

Abstract

This work provides a scheme to investigate the site occupancy and the luminescence properties of lanthanide ions in BaY2Si3O10. The Rietveld refinement of the samples indicates that the lanthanide ions preferably occupy the Y3+ sites in BaY2Si3O10. It is confirmed that valence state of lanthanide ions is stable at +3 in all doping samples. The site-dependent spectroscopic properties of Ce3+ and Eu3+ are studied in VUV–UV–vis spectral region at low temperatures, and the polarization effect on Ce3+ luminescence decay is evaluated. The results indicate that the lanthanide ions experience the similar polarization effect when substituting the Y3+ sites in BaY2Si3O10. The Stokes shift of Ce3+ luminescence becomes larger as Ce3+ doping content increases. Eu3+ f–f line-shape change has not been observed in the spectra as Eu3+ content increases. It demonstrates that the change of the electrostatic binding effect in the lattice has little effect on the ligand polarization of the central lanthanide ion. Finally, a mechanism is proposed to explain why the thermal-quenching of Ce3+ luminescence is negligible in BaY2Si3O10 even if the temperature increases up to 500 K. The influence of dynamic ion–lattice interaction on luminescence properties of the lanthanide ions in BaY2Si3O10 is discussed in detail.

Eu2+ Site Preferences in the Mixed Cation K2BaCa(PO4)2 and Thermally Stable Luminescence

“…Various techniques have been employed to minimize TQ, such as by using high structural rigidity phosphor, ceramic coating (SiO 2 , TiO 2 ) over phosphors, and glass-ceramic phosphors. − In particular, it has been recently demonstrated that crystal defects may play a positive role in diminishing TQ of Eu 2+ luminescence through a possible energy transfer from defect levels to the Eu 2+ 5 d levels owing to an increase of the Na disordering with increasing temperature in the Na 3 Sc 2 (PO 4 ) 3 :Eu 2+ phosphor . It is believed that the mixed cations in a host material could initiate the versatile site occupations of activators, and thus lead to the discovery of new phosphor systems, which is beneficial for optimization of luminescence properties toward practical applications …”

“…18 It is believed that the mixed cations in a host material could initiate the versatile site occupations of activators, and thus lead to the discovery of new phosphor systems, which is beneficial for optimization of luminescence properties toward practical applications. 19 In recent years, our group has proposed a useful methodology for the discovery of new LED phosphors by mineralinspired prototype evolution and new phase construction, which have been effectively applied to the discovery of new phosphors. 20−22 In addition, ABPO 4 :Eu 2+…”

Luminescence and Energy Transfer between Ce3+ and Pr3+ in BaY2Si3O10 under VUV–vis and X-ray Excitation

“…Because of the approximate crystal field strength and nephelauxetic effect of different Ln 3+ ions in sites of the same type of a given host compound, the 4f5d energy splitting of Pr 3+ is generally consistent with that of Ce 3+ in BaY 2 Si 3 O 10 at first glance. Two intense bands are observed above 250 nm in the excitation spectrum of Ba­(Y 0.99 Ce 0.01 ) 2 Si 3 O 10 as displayed in Figure S2, which actually contain three excitation bands and can be assigned to electronic transitions from the Ce 3+ 4f ground state to its first (5d 1 ), second (5d 2 ), and third (5d 3 ) 5d excited states (denoted as 4f–5d 1–3 transitions). ,− Accordingly, bands A and B in Figure a should be attributed to the superposition of Pr 3+ 4f 2 –4f5d 1–3 transitions. To estimate the energies of Pr 3+ 4f 2 –4f5d 1–5 transitions, the 4f–5d J ( J = 1, 2, 3, 4, 5) transitions of Ce 3+ are shifted toward the high-energy direction about 1.51 eV, considering the energy difference between the lowest 5d states of free Ce 3+ (6.12 eV) and Pr 3+ (7.63 eV) .…”

“…BaY 2 Si 3 O 10 , with the monoclinic structure, possesses only one kind of lanthanide (Ln 3+ )-substitutable Y 3+ site with 6-fold coordination . Herein, X-ray diffraction (XRD) patterns of representative samples at room temperature (RT) are displayed in Figure S1.…”

“…BaY 2 Si 3 O 10 , with the monoclinic structure, possesses only one kind of lanthanide (Ln 3+ )substitutable Y 3+ site with 6-fold coordination. 6 Herein, X-ray diffraction (XRD) patterns of representative samples at room temperature (RT) are displayed in Figure S1. No significant second phase can be detected, and all patterns are in accord with the standard pattern, indicating that the dopant Ce 3+ and Pr 3+ ions occupy Y 3+ sites and this substitution has little influence on the crystal structure of studied compounds.…”