Luminescent properties of some ortho- and pentaphosphates doped with Gd3+–Eu3+: Potential phosphors for vacuum ultraviolet excitation

Within the framework of research for new luminescent materials with high quantum efficiency for mercury free lighting devices as well as for plasma display panels, we have studied the rare earth doped phosphates. We have synthesized GdPO4:Eu3+ by solid state reaction at high temperature, LaPO4:Eu3+, Gd3+ by hydrothermal method and LaP5O14:Eu3+, Gd3+ by the flux method. All our pure single-phase samples have been characterized by X-ray diffraction, Raman and Infrared spectroscopies. The excitation and emission spectra were recorded at room temperature. Vacuum ultraviolet (VUV) diffuse reflection spectra show that the forbidden gap of our matrices is close to 160 nm. Unfortunately, excitation spectra revealed that the onset of the charge transfer band of Eu3+ overlaps the 6GJ level of Gd3+, making the quantum cutting process unlikely in these materials.