Synthesis and mechanical properties of low temperature sintered, Sm3+ doped nanoceria electrolyte membranes for IT-SOFC applications

Nanocrystalline Ce0.9Sm0.1O1.95 electrolyte was prepared by nitrate-fuel combustion technique using urea, citric acid, glycine and polyethylene glycol as organic fuels. The combusted precursors were calcined at 700 °C/2 h and then compacted to cylindrical pellets and sintered at 1200 °C for 2, 4 and 6 h durations. The sintered samples were tested for the mechanical hardness and fracture toughness and the results were compared within the fuel sources. Dense nanocrystalline ceria electrolyte membranes having theoretical sintered densities of 98% and the sintered grain sizes below 1 μm were successfully achieved at 1200 °C. Ceria electrolytes derived from the glycine and citric acid fuels have maximum microhardness of 7.94 ± 0.2 and 7.63 ± 0.2 GPa. Whereas high toughness is observed for the samples prepared from the urea and polyethylene glycol fuels. They were estimated as 3.06 ± 0.3 and 3.17 ± 0.3 MPa m1/2 respectively at 20 N. The study significantly contributes to select the fuels appropriately so that the advantages of low temperature densification and mechanically durability can be achieved in ceria electrolyte membranes for IT-SOFC applications.