[en] The storage of high level radioactive waste in deep geological repositories is an issue of international research in countries with nuclear reactors. A major risk is the groundwater infiltration, which can cause degradation of the containers and leaching the radioactive waste through the different barriers. The study of materials for use as engineered barriers is fundamental, because if dissolution is present, the elements can be captured, ensuring that radioactive materials do not disperse off. The work is divided in four parts, the first describes the techniques developed for the synthesis of phosphates: NaZr₂(PO₄) [NZP] and τ-Zr(Na_0.06H_0.94PO₄)₂ [TZP-Na], their chemical and morphological characterization, thermal stability and surface area. The obtained NZP shows a diffraction diagram similar to the Jcpds pattern, it has a surface area of 4.9±0.1 m²·g^-1. There are not reports of diffraction patterns for TZP-Na, which has a surface area of 22.9±0.40 m²·g^-1. The hydrogenphosphate obtained, τ-Zr(HPO₄)₂, shows a diffraction diagram similar to that reported by Nor by. The second part presents the physicochemical characterization of the phosphates surface. The constants of formation of surface sites and their distribution were calculated using FITEQL 4.0. The sites surface density (d_s) were determined from potentiometric titration curves of phosphate, hydrogen phosphate and NaClO₄ 0.5 M; d_s were 3.2 sites nm^-2 for NZP and 2.1 sites·nm^-2 for TZP-Na. The values of curves formation constants for surface sites were, for NZP: K _1P-O=2, K_2P-O=-7, K_1Zr-O=6.11, K_1Zr-O=7.94, and for TZP-Na: K_1P-O=5.14, K_2P-O=-7.03, K_1Zr-O=2.60, K_1Zr-O=-9.85. The third part of the work reports the samarium and europium sorption curves on phosphate and on hydrogenphosphate at different ph values. The values of the curves were fed on FITEQL 4.0 program and NZP surface complexation constants were obtained. The results for the NZP show, for both lanthanides, a monodentate complex at the zirconium site and a bidentate complex on the phosphate site. The fourth part of the research reports on the stability of phosphate and hydrogenphosphate to gamma radiation, with doses of: 10, 30 and 50 MGy. The NZP irradiated at 50 MGy showed very slight changes in their morphology, which changed to hexagonal sheets to cubic form; heating the irradiated NZP regenerates the original morphology. The irradiated TZP-Na showed changes in its crystalline structure but without becoming amorphous, however it maintained its chemical and morphology structure. In conclusion, both phosphates, NaZr₂(PO₄) and τ-Zr(Na_0.06H_0.94PO₄)₂, may be considered for sorption of lanthanides in the barriers, even though the NZP is more resistant to radiation. (Author)