RbBaPO4:Eu2+ phosphors have been prepared by a high-temperature solid-state reaction method, and the structure was determined by Rietveld refinement based on powder X-ray diffraction (P-XRD) data. Their VUV-UV-vis photoluminescence properties are systematically investigated with three objectives: (1) based on low-temperature spectra, we clarify the site occupancies of Eu2+, and demonstrate that the doublet emission bands at ∼406 and ∼431 nm originate from Eu2+ in Ba2+ [Eu2+(I)] and Rb+ [Eu2+(II)] sites, respectively; (2) an electron-vibrational interaction (EVI) analysis is conducted to estimate the Huang-Rhys factors, the zero-phonon lines (ZPLs) and the Stokes shifts of Eu2+ in Rb+ and Ba2+ sites; (3) the studies on luminescence decay of Eu2+(I) reveal that dipole-dipole interaction is mainly responsible for the energy transfer from Eu2+(I) to Eu2+(II), and the energy migration between Eu2+(I) is weak. Finally, the X-ray excited luminescence (XEL) spectrum indicates that the light yield of the sample RbBa0.995Eu0.005PO4 is ∼17700 ph/MeV, showing its potential application in X-ray detecting. @en

Ce3+ and Eu2+ doped and Ce3+-Eu2+ co-doped Sr2MgSi2O7 phosphors are prepared via a high-temperature solid-state reaction technique. The synchrotron radiation vacuum ultraviolet-ultraviolet (VUV-UV) excitation and ultraviolet-visible (UV-vis) emission spectra of diluted Ce3+ and Eu2+ doped Sr2MgSi2O7 samples are measured at cryogenic temperatures. The electron-vibrational interaction (EVI) between Ce3+ and its surroundings is analyzed. The dependencies of the 4f-5d transitions of Ce3+ on the structure of the host compounds Sr2MgSi2O7, Ba2MgSi2O7 and BaMg2Si2O7 are discussed in detail. Then the thermal quenching channel is proposed based on the measurements of temperature dependent luminescence intensities and decay times of Ce3+ and Eu2+ in Sr2MgSi2O7, and the Ce3+ → Eu2+ energy transfer mechanism is understood by three luminescence dynamic models. In addition, Sr2MgSi2O7:Ce3+/Eu2+ samples are evaluated for the possibilities of X-ray detection applications using X-ray excited luminescence (XEL) spectroscopy, and it was found that they are not suitable.@en

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+emission and valence stability of both Eu2+/Eu3+ions in CaMgSi2O6are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ions for anti-counterfeiting applications.@en