Direct addition of lithium and cobalt precursors to Ce0.8Gd0.2O1.95 electrolytes to improve microstructural and electrochemical properties in IT-SOFC at lower sintering temperature

To improve the microstructural and electrochemical properties of gadolinium-doped ceria (GDC) electrolytes, materials co-doped with 0.5–2 mol% of lithium and cobalt oxides were successfully prepared in a one-step sol gel combustion synthesis route. Vegard's slope theory was used to predict the dopant solubility and the sintering behaviour. The charge and size of the added dopant influence the atom flux near the grain boundary with a change in the lattice parameter. In fact, compared to traditional multi grinding steps, sol gel combustion facilitates molecular mixing of the precursors and substitution of the dopant cations into the fluorite structure, considerably reducing the sintering temperature. Adding precursors of lithium and cobalt, as dopant, increases the GDC densification and reduces its traditional sintering temperature down to 1000–1100 °C, with an improvement of electrochemical properties. Impedance analysis showed that the addition of 2 mol% of lithium or 0.5 mol% of cobalt enhances the conductivity with a consequent improvement of cell performances. High total conductivities of 1.26·10−1 S cm−1 and 8.72·10−2 S cm−1 at 800 °C were achieved after sintering at 1000 °C and 1100 °C for 2LiGDC and 0.5CoGDC, respectively.