Two alternative chemical synthesis methods—cryotechnological coprecipitation of hydroxides and cocrystallization of salts—were used for preparing (CeO₂)_1–x(Y₂O₃)_x nanopowders (x = 0.10, 0.15, 0.20) with a mean coherent scattering domain size of ~7–11 nm and S_sp = 2.1–97.5 m²/g. From these nanopowders, ceramic nanomaterials with mean coherent scattering domain sizes of ~61–85 nm were synthesized. It was studied how the phase composition, microstructure, and electrical transport properties of the produced samples depend on the Y₂O₃ content of a CeO₂-based solid solution and on the synthesis method. It was shown that, in the series (CeO₂)_1–x(Y₂O₃)_x (x = 0.10, 0.15, 0.20), the solid solution (CeO₂)_0.90(Y₂O₃)_0.10 has the highest ionic conductivity with the ion transport number t_i = 0.73 (600°C). In its physicochemical characteristics, this ceramic can be used as a solid electrolyte of intermediate-temperature fuel cells.