In the present study powders with empirical formula Ce1-xGdxO2-x/2 (x = 0, 0.1, 0.3, 0.5, 0.7) were synthesized using a method of ionic gelation at room temperature. This technique involves mixing initial aqueous solutions of sodium alginate and cerium-gadolinium nitrates in appropriate ratios, followed by heat treatment of the resulting gel at 500 °C. The obtained powders were pressed into pellets and sintered at 1400 °C for 3 h to produce ceramics. The phase composition of the powders and ceramics was investigated by X-ray diffraction (XRD). The obtained results demonstrate a partial substitution of cerium with gadolinium ions in the cerium oxide crystal lattice, evidenced by a shift of the diffraction peak maxima to lower angles as a result of the increase in the lattice parameter. Electron paramagnetic resonance (EPR) spectroscopy was performed to study the oxidation state of powdered materials and high-temperature ceramics. The presence of Ce3+ was indicated in the undoped CeO2. The evolution of the peak-to-peak linewidth (ΔHpp) profile shows a dependence on the dopant concentration in the ceria lattice.