Feasibility and mechanism of lithium oxide as sintering aid for Ce0.8Sm0.2Oδ electrolyte

Cerium oxide is a promising material for electrodes and electrolytes of solid oxide fuel cells (SOFCs). Lowering the sintering temperature of the electrolyte will bring a lot of benefits to the fabrication of SOFCs. This paper evaluates the feasibility of using lithium oxide as a sintering aid to reduce the densification temperature of samarium-doped ceria (Ce0.8Sm0.2O1.9, SDC) by SEM and electrochemical impedance spectroscopy. It is shown that the addition of Li2CO3 can indeed decrease the sintering temperature of SDC. More attention is paid to understand the aiding mechanism of Li2CO3. Raman spectroscopy and thermal analysis indicate that it is Li2O, a decomposition product of Li2CO3, that facilitates the sintering by way of a liquid phase sintering effect on the grain boundaries of SDC. These findings help to promote the application of ceria-based electrolytes for intermediate temperature SOFCs.

► Addition of Li2CO3 drastically lowers the densification temperature of SDC. ► Addition of Li2CO3 changes neither the structure nor the bulk conductivity of SDC. ► The melting and evaporating of Li2O enhance the grain boundary conductivity of SDC at low sintering temperatures. ► Li2O facilitates the sintering by way of a liquid phase sintering mechanism.