Tuning of phosphor luminescence properties, including the emission energy/intensity and thermal stability, is an important way to develop superior luminescent materials for diverse applications. In this work, we discuss the effect of band gap engineering and energy transfer on the luminescence properties of Ce³⁺ or Pr³⁺ doped (Y,Gd)AGG systems, and analyze the underlying reasons for their different phenomena. By using VUV-UV excitation spectra and constructing VRBE schemes, the changes of host band structure, 5d excited level energies and emission thermal stability of Ce³⁺ and Pr³⁺ with the incorporation of Gd³⁺ ions were studied. In addition, the energy transfer dynamics was also investigated in terms of the luminescence decay curves. This work demonstrates a way to tune phosphor luminescence properties by combining band gap engineering and energy transfer tailoring and provides an inspiring discussion on the different results of Gd³⁺ doping on the Ce³⁺ and Pr³⁺ emissions.

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.