P-239: Synthesis and Photoluminescence Properties of Tb3+-Doped Lanthanide Orthophosphates (La1−xGdx)0.94Tb0.06PO4 (0.5≤x≤1.0)

The photoluminescence properties of the (La1−xGdx)0.94Tb0.06PO4 (0.5≤x≤1.0) phosphors synthesized by ultrasonic spray pyrolysis were investigated under VUV irradiation. In order to understand the effect of Gd addition on the photoluminescence properties, we obtained the excitation and emission spectra of the (La1−xGdx)0.94Tb0.06PO4 phosphors with various Gd contents. Annealed (La1−xGdx)0.94Tb0.06PO4 phosphors showed a smooth, regular, and spherical morphology. The XRD spectra of the (La1−xGdx)0.94Tb0.06PO4 showed the solid solutions of the constituent lanthanide phosphates, which crystallized in a monoclinic monazite. The XRD peaks shifted slightly toward higher angles with increasing Gd content, indicating that the lattice parameter slightly decreased with an increase in Gd content. The phosphors emitted the green light due to the transition from 5D4 to 7Fj (j=3−6) at 489, 543, 585, and 621nm, respectively. (La0.25Gd0.75)0.94Tb0.06PO4 showed the strongest emission intensity.