Fast oxide ion conducting Ce1-xMxO2-delta (M = In, Sm; x = 0.1, 0.2) and Ce0.8Sm0.05Ca0.15O1.825 were prepared from the corresponding perovskite-like structured materials with nominal chemical composition of BaCe1-xMxO3-delta and BaCe0.8Sm0.05Ca0.15O2.825, respectively, by reacting with CO2 at 800 degrees C for 12 h. Powder X-ray diffraction (PXRD) analysis showed the formation of fluorite-type CeO2 and BaCO3 just after reaction with CO2. The amount of CO2 gained per ceramic gram was found to be consistent with the Ba content. The CO2 reacted samples were washed with dilute HCI and water, and the resultant solid product was characterized structurally and electrically employing various solid-state characterization methods, including PXRD, and alternating current (ac) impedance spectroscopy. The lattice constant of presently prepared Ce1-xMxO2-(delta) and Ce0.8Sm0.05Ca0.15O1.825 by a CO2 capture technique follows the expected ionic radii trend. For example, In-doped Ce0.9In0.1O1.95 (In-(VIII)(3+) = 0.92 angstrom) sample showed a fluorite-type cell constant of 5.398(1) angstrom, which is lower than the parent CeO2 (5.411 angstrom, Ce-(VIII)(4+) = 0.97 angstrom). Our attempt to prepare single-phase In-doped CeO2 samples at 800, 1000, and 1500 degrees C using the ceramic method was unsuccessful. However, we were able to prepare single-phase Ce-0.9,In0.1O1.95 and Ce0.8In0.2O1.9 by the CO2 capture method from the corresponding barium perovskites. The PXRD studies showed that the In-doped samples are thermodynamically unstable above 800 degrees C. The ac electrical conductivity studies using Pt electrodes showed the presence of bulk, grain-boundary, and electrode contributions over the investigated temperature range in the frequency range of 10(-2)- 10(7) Hz. The bulk ionic conductivity and activation energy for the electrical conductivity of presently prepared Sm- and (Sm + Ca)-doped CeO2 samples shows conductivities similar to those of materials prepared by the ceramic method reported in the literature. For instance, the conductivity of Ce0.8Sm0.2O1.9 using the CO2 capture technique was determined to be 4.1 x 10(-3) S/cm, and the conductivity of the same sample prepared using the ceramic method was 3.9 x 10(-3) S/cm at 500 degrees C. The apparent activation energy of the area-specific polarization resistance for the symmetric cell (Sm,Sr)CoO3-x,vertical bar Ce0.8Sm0.2O1.9 vertical bar(Sm,Sr)CoO3-x(Sm,Sr)CoO3-x was determined to be eV in air.