Preparation of ultra-fine Sm0.2Ce0.8O1.9 powder by a novel solid state reaction and fabrication of dense Sm0.2Ce0.8O1.9 electrolyte film

A novel solid state reaction was adopted to prepare Sm0.2Ce0.8O1.9 (SDC) powder. A mixed oxalate Sm0.2Ce0.8(C2O4)1.5·2H2O was synthesized by milling a mixture of cerium acetate hydrate, samarium acetate hydrate, and oxalic acid for 5 h at room temperature. An ultra-fine SDC powder with the primary particle size of 5.5 nm was obtained at 300 °C. The ultra-low temperature for the formation of SDC phase was due to the atomic level mixture of the Sm3+ and Ce4+ ions. The crystal sizes of SDC powders at 300 °C, 550 °C, 800 °C, and 1050 °C were 5.5 nm, 11.4 nm, 24.1 nm and 37.5 nm, respectively. The sintering curves showed that the powder calcined at lower temperature was easier to be sintered owning to its smaller particle size. A solid oxide electrolytic cell (SOEC), comprising porous La0.8Sr0.2Cu0.1Fe0.9O3−δ (LSCF) for substrate, LSCF–SDC for active electrode, SDC for electrolyte, and LSCF–SDC for symmetric electrode, was fabricated by dip-coating and co-sintering techniques. An extremely dense SDC film with the thickness of 20 μm was obtained at only 1200 °C, which was about 100–300 °C lower than the literatures׳ reports. The designed SOEC was proved to work effectively for decomposing NO (3500 ppm, balanced in N2), 80% NO can be decomposed at 600 °C.