Ultrafine-grained (∼148 nm) and microcrystalline (∼1.5 μm) Sm0.2Ce0.8O2−δ (SDC20) ceramic pellets with relatively high density are fabricated by two-step sintering (TSS) and the conventional sintering (CS) method. The electrical conductivity was studied at intermediate temperatures in the range of 300–600 °C, and concentration cell measurements were employed to investigate the interfacial effect at or near the grain-boundaries of ultrafine-grained SDC20. The results show that ultrafine-grained SDC20 has a remarkable enhancement in the total conductivity of about one order of magnitude greater than that of conventional microcrystalline SDC20 mainly due to the predominance of increased grain-boundary conduction with decreasing grain size. Concentration cell measurements under different partial pressure of oxygen (PO2) prove that the enhanced grain-boundary conductivity of ultrafine-grained SDC20 is mainly attributed to purely ionic charge carriers but not electronic contribution. The interfacial effect is due most likely to enhanced mobility of oxygen vacancies at or near the grain boundaries. Two-step sintering of SDC20 electrolytes provides an effective approach for further development of high performance, low operation temperature solid oxide fuel cells.
Sun, H., Rainwater, B. H., Xiong, X., Chen, Y., Wei, T., Zhang, Q., … Liu, M. (2017). Interfacial effects on electrical conductivity in ultrafine-grained Sm0.2Ce0.8O2−Δ electrolytes fabricated by a two-step sintering process. International Journal of Hydrogen Energy, 42(16), 11823–11829. https://doi.org/10.1016/j.ijhydene.2017.03.151