Investigation on La3+ and Dy3+ co-doped ceria ceramics with an optimized average atomic number of dopants for electrolytes in IT-SOFCs

Abstract In the present study, we investigate the fundamental properties of CeO 2 by selecting La 3+ (57), and Dy 3+ (66) as dopants with optimized average atomic number of 61.5, which lies in between Pm 3+ (62) and Sm 3+ (62) in accordance with the criteria for optimum doping. A system of co-doped ceria ceramics Ce 1–x–y La x Dy y O 2-δ ((x, y) = (0.00, 0.00), (0.025, 0.025), (0.05, 0.05), (0.075, 0.075), (0.10, 0.10), (0.00, 0.20) and (0.20, 0.00)) as electrolytes for intermediate temperature solid oxide fuel cells were successfully prepared by a well-known sol-gel auto-combustion route. In order to obtain dense samples, the prepared pellets were sintered in air at 1300 °C for 4 h using conventional furnace and relative densities of all the samples were found to be higher than 95%. Single phase cubic structure, microstructural density and elemental composition analysis of all the samples were studied by powder X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy techniques, respectively. Raman spectroscopy analysis confirmed the formation of concentrated O 2- –vacancies in the co-doped ceria system. Impedance spectroscopy measurements revealed the high value of total ionic conductivity and low activation energy for the composition Ce 0.85 La 0.075 Dy 0.075 O 2−δ i.e., 2.08 × 10 –2 S cm –1 and 0.58 eV, respectively. Linear thermal expansion analyses of all the samples revealed the matched thermal expansion coefficients. Finally, these results recommend that the Ce 0.85 La 0.075 Dy 0.075 O 2−δ sample can be useful as a solid electrolyte in IT-SOFC applications.