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Enhanced Ionic Conductivity in Ce 0.8 Sm 0.2 O 1.9 : Unique Effect of Calcium Co‐doping
Author(s) -
Banerjee S.,
Devi P. S.,
Topwal D.,
Mandal S.,
Me K.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600890
Subject(s) - materials science , conductivity , analytical chemistry (journal) , doping , x ray photoelectron spectroscopy , sintering , ionic conductivity , oxide , electrical resistivity and conductivity , ion , chemistry , chemical engineering , metallurgy , optoelectronics , chromatography , electrode , electrolyte , engineering , electrical engineering , organic chemistry
In order to identify new oxide ion‐conducting materials in the ceria family of oxides, the unique effect of co‐doping is explored and a novel series of Ce 0.8 Sm 0.2– x Ca x O 2–δ compositions is identified that have enhanced properties compared to the single‐doped Ce 0.8 Sm 0.2 O 1.9 and Ce 0.8 Ca 0.2 O 1.9 compositions. Moreover, the superior characteristics of the co‐doped Ce 0.8 Sm 0.2– x Ca x O 2–δ powders prepared by the mixed‐fuel process aid in obtaining 98 % dense ceramics upon sintering at 1200 °C for 6 h. Though a linear increase in conductivity is observed by replacing Sm with Ca, the composition with the maximum amount of Ca and the minimum amount of Sm exhibits a significant improvement in properties compared to the rest in the series. The composition Ce 0.80 Sm 0.05 Ca 0.15 O 2–δ exhibits a conductivity as high as 1.22 × 10 –1 S cm –1 at 700 °C with minimum activation energy (0.56 eV) and a superior chemical stability to reduction compared to any of the hitherto known (CaSm) compositions. The absence of Ce III , confirmed both from X‐ray photoelectron spectroscopy and X‐ray absorption spectroscopy, strongly suggests that the observed increase in conductivity is solely due to the oxide ion conductivity and not due to the partial electronic contribution arising from the presence of Ce III and Ce IV . To conclude, the experimental results on the Ce 0.8 Sm 0.2– x Ca x O 2–δ series underscore the unique effect of calcium co‐doping in identifying a cost‐effective new composition, with a remarkably high conductivity and enhanced chemical stability to reduction, for technological applications.