This paper addresses the formulae-related enhancement of the GdxY1-xPO4:Tb3+ nanopowders when submitted to (VUV) vacuum ultraviolet. Structural characterizations of GdxY1-xPO4:Tb3+ nanocrystals were conducted by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In particular, for the first time, in this work, the photoluminescence upon VUV excitation of GdxY1-xPO4:Tb3+ powders synthesized by the solvothermal method, is reported, and the optical study reveals that the photoluminescent properties of nanophosphors are strongly dependent on their crystalline structures, as well as on gadolinium-yttrium composition. The highest emission intensity upon 160 nm radiation was observed for the Gd0.5Y0.5PO4:Tb3+ powders which exhibited a two-fold increase in luminescence intensity comparing with YPO4:Tb3+.