Site-Selective Eu³⁺ Luminescence in the Monoclinic Phase of YSiO₂N

Abstract

Eu 3+ -doped YSiO 2 N phosphor was synthesized, and its crystal structure was analyzed by single-crystal X-ray and neutron powder diffraction techniques. The new crystal structure of YSiO 2 N with the monoclinic lattice (space group C2/c) composed of nonequivalent [YO 6 N 2 ] dodecahedra was identified, and, in this structure, five different Y 3+ sites take C i or C n symmetry. Based on the experimentally determined crystal structure, we characterized the luminescence properties of the Eu 3+ ions with site-selective and time-resolved spectroscopy. The Eu 3+ ions at the Y: C n sites show intense 5 D 0 → 7 F 2 electric dipole luminescence peaking at 626 nm with a short lifetime (0.61 ms) due to the lack of inversion center. In the centrosymmetric C i sites, the lifetime of the 5 D 0 level was quite long (5.51 ms), and the strongest three peaks are assigned to the 5 D 0 → 7 F 1 magnetic dipole transition instead of 5 D 0 → 7 F 2 . The anomalous temperature dependence of the long lifetime for Eu 3+ : 5 D 0 at this C i site at low temperatures suggests that the slow radiative rate can be influenced by the thermal distortion of centrosymmetry. The thermal quenching mechanism of the Eu 3+ : 5 D 0 luminescence at both sites is considered to be due to the charge transfer states related to the N 3− ions in the [Eu 3+ O 6 N 2 ] dodecahedra rather than the multiphonon relaxation mechanism. This study shows the potentials of Eu 3+ luminescence in oxynitride coordination and provides new insights into the material design guidelines for near-UV excitable red phosphor activated with Eu 3+ ions.

Synthesis of Eu(HCOO)$_3$ and Eu(HCOO)$_{3}\cdot$(HCONH$_2$)$_2$ crystals and observation of their $^5$D$_{0}\rightarrow ^{7}$F$_0$ transition for quantum information systems

“…Both compounds show an increase in lifetime with decreasing temperature. An increase is common in Eu 3+ compounds [45][46][47][48][49][50][51], but this trend is occasionally not consistent [52,53], notably in the case of EuCl 3 ⋅6H 2 O [14, 44].…”

Deep‐Red Ca3Al2Ge3O12:Eu3+ Garnet Phosphor with Near‐Unity Internal Quantum Efficiency and High Thermal Stability for Plant Growth Application

“…Furthermore, the intensive 5 D 0 → 7 F 4 transition can be assigned to the coordination polyhedron of EuOx distorted from a cubic geometry to the square antiprism, where the 5 D 0 → 7 F 2 transition is forbidden due to the point group selection rule, while the 5 D 0 → 7 F 4 transition is allowed. [18,[41][42][43] Generally, most of the reported Eu 3+ -doped phosphors emit red light with the 5 D 0 → 7 F 2 transition as the dominant one. To date, only a handful of Eu 3+ -doped phosphors can emit intense deep-red luminescence at around 707 nm ascribed to an intense 5 D 0 → 7 F 4 transition, represented by LaPO 4 :Eu 3+ , [44] Na 3 YSi 3 O 9 :Eu 3+ , [45] Ca 2 Ga 2 SiO 7 :Eu 3+ , [46] Bi 2 SiO 5 :Eu 3+ , [47] and Ca 2 Ga 2 GeO 7 :Eu 3+ .…”

Control of the Emission and Excitation Energies in Pr3+-Activated Perovskite Oxide–Oxynitrides by Bandgap Engineering

“…26,27 In addition, when a small amount of Eu 3+ was substituted in the host lattice, Eu 3+ can be excited via charge transfer between the VB of the host material and 4f level of Eu 3+ . 28,29 Thus, the excitation process due to the indirect excitation of Ln 3+ via the host lattice should be suitable for f−f emission in white LED applications.…”

“…This excitation process facilitates a strong f – f emission of Ln 3+ because the electron transitions between the valence band (VB) and conduction band (CB) of the host materials and/or between Ln 3+ and CB are allowed in principle. For example, the strong f – f emissions of Eu 3+ and Tb 3+ have been reported by asymmetrically coordinating multiple organic ligands to Eu 3+ and Tb 3+ and using the electronic transition between the highest occupied molecular orbital and lowest unoccupied molecular orbital of the organic molecules in the excitation process. , In addition, when a small amount of Eu 3+ was substituted in the host lattice, Eu 3+ can be excited via charge transfer between the VB of the host material and 4 f level of Eu 3+ . , Thus, the excitation process due to the indirect excitation of Ln 3+ via the host lattice should be suitable for f – f emission in white LED applications.…”