Sr2+-Gd3+ co-doped CeO2: A cost-effective variant for IT-SOFC electrolytes

Abstract Cost effective Ce 1−x−y Sr x Gd y O 2−δ ceramics are developed and compared with Ce 0.85 Gd 0.15 O 2−δ , in terms of their electrical properties. The amount of expensive Gd 3+ is aimed to reduce by co-doping of low cost 2.5-5 mol% Sr 2+ . Powder x-ray diffraction confirmed the single fluorite structure (space group Fm-3 m) in all the prepared samples. The vital essence of the present study is that a slight Sr 2+ co-doping allowed us to reduce a significant Gd 3+ doping amount, with a gain in ionic conductivity, compared to Ce 0.85 Gd 0.15 O 2−δ . For instance, Ce 0.875 Sr 0.025 Gd 0.10 O 2−δ solid solution displayed the ionic conductivity, higher than Ce 0.85 Gd 0.15 O 2−δ with 5 mol% low Gd 3+ amount. The total electrical conductivities were found to be almost 1 000-10 000 times higher than electronic conductivity at air p (O 2 ) i.e. 0.21 bar, confirming the dominating ionic conduction. However, at extremely low p (O 2 ) , the samples show a mixed-ionic electronic conduction (MIEC) behaviour due to Ce 4+ to Ce 3+ reduction.