Improvement of luminescent properties of GdPO4 doped with optimal europium concentration by Co-doping with lanthanum

Hexagonal gadolinium Phosphate Hydrate doped with different europium amounts (Gd_1-xPO₄:Eu_x·H₂O; x = 0.01, 0.05, 0.10, 0.15, and 0.20) was synthesized by hydrothermal synthesis method and the obtained samples were analyzed giving the optimal dopant concentration. Furthermore, gadolinium was additionally replaced by Lanthanum Gd_0.85-yLa_yPO₄:15%Eu (y = 0.25, 0.5, 0.75) in hopes of improving luminescence properties even more. This may be possible due to the fact that LaPO₄ exhibits a monoclinic crystal structure, which usually shows better luminescence properties. All of the synthesized compounds were analyzed by X-ray diffraction in order to investigate their crystal structure. SEM analysis was used to characterize the morphology of synthesized particles, while surface area and the pore size of Gd_0.85-xLa_xPO₄:15%Eu samples were measured using Nitrogen adsorption by the BET method and BJH method. The luminescence properties were also characterized and discussed in detail. Lastly, the cytotoxicity study demonstrated that the replacement of gadolinium with lanthanum leads to a reduction in the toxicity of the samples.