Sintering of Samarium-doped ceria powders prepared by a glycine-nitrate process

This work investigates the sintering characteristics and electrical properties of SDC electrolytes prepared with glycine-nitrate-combustion derived powders, which are often used for fabricating dense SDC electrolyte films using a dry-pressing process. The compact powders show the highest sintering rate at 730 °C and are sintered to 90.7% of theoretical density at 1300 °C for 5 h. However, using the powder as the precursor, SDC films can be sintered to be much denser (about 99% of the theoretical density) even at 1250 °C when the electrolyte layers are co-sintered with NiO-SDC substrates. In addition to increased density, increasing the sintering temperature causes enlargement of crystalline parameters, which is possibly due to the reduction of Ce4+ to Ce3+. The reduction is associated with the formation of oxygen vacancies, which might cause defect-association and thus promote the activation energy for oxygen-ion conduction. It is found that the conductivity increases with the sintering temperature to its maximum when SDC is sintered at 1300 °C.