Intense hypersensitive luminescence of Eu3+-doped YSiO2N oxynitride with near-UV excitation

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

“…For the assignment of Eu 3+ : 4f–4f PL and PLE bands at different sites, the general relationship between spectroscopic features and crystallographical structure for Eu 3+ ions is summarized in Table . Under the CT excitation, the spectral shape is almost the same as the reported one . The five luminescence peaks in the range of 16 600–17 200 cm –1 are assigned to the 5 D 0 → 7 F 1 magnetic dipole (MD) transition.…”

“…Powders of starting chemicals were mixed with a ball milling system (Premium Line P-7, Fritsch) with ethanol (>99.5%). The obtained slurry was dried at 120 °C for 24 h. The mixture was pelletized with dry pressing and sintered at 1600 °C under N 2 gas flow for 24 h. Because Eu 3+ ions in the as-made samples were partially reduced into Eu 2+ states, the Eu 3+ -doped as-made samples were annealed at 700 °C under N 2 gas flow for 24 h to oxidize reduced europium ions, according to the Ellingham diagram. , …”

“…The other ambiguous point is the assignment of the split CT excitation bands. Previously, we concluded the assignment of the broad excitation bands to be the CT transition from N 3– and O 2– to Eu 3+ . Considering that the Eu 3+ luminescence depends on the occupying sites, we have to take another possibility into account; the CT transition from only N 3– in crystallographically different sites.…”

“…For the purpose of extending the CT excitation toward longer wavelengths, we fabricated the Eu 3+ -doped oxynitride sample, YSiO 2 N:Eu 3+ , and reported its luminescence properties . Compared with other Eu 3+ -doped oxides (α-CaSiO 3 :Eu 3+ , α-Y 2 Si 2 O 7 :Eu 3+ , and y -Y 2 Si 2 O 7 :Eu 3+ ), YSiO 2 N:Eu 3+ showed the CT excitation bands red-shifted over 9500 cm –1 and the 2.7–6.0 times stronger 5 D 0 → 7 F 2 luminescence (at 626 nm) due to partial N 3– coordination.…”

Deep-red to near-infrared luminescence from Eu2+-trapped exciton states in YSiO2N

“…Previously, we reported the intense red luminescence of the Eu 3+ -doped YSiO 2 N phosphor under near-UV excitation. 30,31 While the as-made YSiO 2 N:Eu 3+ sample, which was prepared by a solid-state reaction at 1600 1C under a N 2 gas flow, showed a strong absorption band in the range of 380-500 nm and weak Eu 3+ luminescence, the annealing process of the sample at 700 1C under a N 2 gas flow successfully enhanced the Eu 3+ luminescence intensity. 30 According to the Ellingham diagram, 32 this enhancement was possibly due to the oxidization of Eu ions that were reduced into the divalent state during high-temperature synthesis under an inert atmosphere.…”