Effect of nitrogen substitution on luminescence tuning in garnets

Phys. Chem. Chem. Phys., 2020,22, 9513-9517. https://doi.org/10.1039/D0CP00586J

Anionic substitution is attracting research interest as a property modulation strategy. Although the effect of nitrogen incorporation on luminescence tuning has been widely reported, the correlation between dodecahedral expansion on Si4+–N3− co-substitution and crystal-field splitting of Ce3+ in garnets is rarely discussed. This work is devoted to unraveling the structure–property relationship between anionic substitution and spectroscopy tuning. Ligand movement patterns of a dodecahedron and an octahedron are investigated for tetragonal distortion and inter-facial distance, both of which indicate an energy level shift originating from the crystal-field effect. The quantitative crystal-field calculation is performed on the basis of ligand coordinates to derive the analytical expression for further confirmation. This work complements the substitution effects of both cationic and anionic chemical species on spectral tuning in garnets, and will be helpful in material design and property modulation of garnet-based luminescent materials.

Enhanced persistent luminescence via Si4+ co-doping in Y3Al2Ga3O12:Ce3+, Yb3+, B3+

J. Lumin., 2020, 222, 117190. https://doi.org/10.1016/j.jlumin.2020.117190.

Persistent luminescence phosphors with long duration and high emitting intensity have attracted considerable attention for applications in safety signage and energy storage. Herein, we successfully introduce non-equivalent ions Si4+ into Al3+ sites in the garnet phosphor Y3Al2Ga3O12:Ce3+,Yb3+,B3+ by conventional solid-state reaction. The persistent luminescence duration has been dramatically enhanced over 40 h at the 0.32 mcd/m2 threshold value after visible light radiation, almost twice longer than the sample without Si4+. Moreover, the afterglow emission intensity of the persistent luminescence is also improved. We confirm that the synthesized phosphors possess not only deeper trap depth but also wider trap distribution and higher trap density after the cooperation of Si4+. The initial rise approach is used by performing a series of thermoluminescence analyses at various temperatures after 432 nm excitation, which demonstrates the exact trap distribution from 0.47 to 1.11 eV. At the end, the mechanism of the persistent luminescence is depicted using a schematic energy diagram of the vacuum referred binding energy of Y3Al2Ga3O12.

Insight into the Relationship between Crystal Structure and Crystal-Field Splitting of Ce3+ Doped Garnet Compounds

J. Phys. Chem. C., 2018, 122, 6, 3567–3574. https://doi.org/10.1021/acs.jpcc.7b12826

The common understanding of the negative relationship between bond lengths and crystal-field splitting (CFS) is renewed by Ce3+ doped garnets in this work. We represent the contradictory relationship between structure data and spectroscopic crystal-field splitting in detail. A satisfactory explanation is given by expressing crystal-field splitting in terms of crystal-field parameters, on the basis of structural data. The results show that not only the bond length, but also the geometrical configuration have influence on the magnitude of crystal-field splitting. Also it is found that the ligand oxygen behaves differently with regard to multiple site substitution in garnet structure.