Structural and photoluminescence properties of Eu3+-doped (Y2.99-xGdx)Al5O12 phosphors under vacuum ultraviolet and ultraviolet excitation

Eu-doped (Y2.99-xGdx)Al5O12 phosphors (with x = 0, 0.5, 1, 1.5, 2, 2.5, and 2.99) were prepared by a sol-gel method using polyvinylalcohol (PVA) as gel agent. The crystal structures were characterized through X-ray diffraction and the resulting data were refined by the Rietveld method, which shows a linear increase of the lattice parameter with the Gd content. Further structural characterization was carried out via Raman spectroscopy. The effect of substituting Y3+ by Gd3+ on the Eu-doped Y3Al5O12 (YAG) photoluminescence properties was investigated using vacuum ultraviolet (VUV) and ultraviolet (UV) excitation. The excitation and emission spectra of the produced (Y2.99-xGdx)Al5O12 phosphors indicate that their luminescence properties are strongly dependent on the Gd3+ substitution. Our results also reveal a nonlinear decrease in the band-gap of these materials by increasing the Gd concentration.