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Doped Germanate‐Based Apatites as Electrolyte for Use in Solid Oxide Fuel Cells
Author(s) -
Wang S.F.,
Hsu Y.F.,
Lin W.J.,
Kobayashi K.
Publication year - 2014
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201300093
Subject(s) - materials science , sintering , electrolyte , ceramic , oxide , solid oxide fuel cell , chemical engineering , electrochemistry , fuel cells , inorganic chemistry , mineralogy , metallurgy , chemistry , electrode , engineering
Apatite ceramics, known for their good electrical conductivities, have garnered substantial attention as an alternative electrolyte for solid oxide fuel cells (SOFCs). However, studies focusing on the electrochemical performances of SOFCs with apatities as electrolytes remain rare, partly due to their high sintering temperature. In this study, the effects of Mg 2+ , Al 3+ , Ga 3+ , and Sn 4+ dopants on the characteristics of La 9.5 Ge 6 O 26 ± δ are examined and their potential for use as SOFC electrolytes evaluated. The results indicate that La 9.5 Ge 5.5 Al 0.5 O 26 is stabilized into a hexagonal structure, while the La 9.5 Ge 5.5 Sn 0.5 O 26.25 , La 9.5 Ge 5.5 Ga 0.5 O 26 , and La 9.5 Ge 5.5 Mg 0.5 O 25.75 ceramics reveal triclinic cells accompanied with the second phase La 2 Sn 2 O 7 or La 2 GeO 5 . The study further demonstrates that a high sintering temperature is needed for both the La 9.5 Ge 5.5 Mg 0.5 O 25.75 and the La 9.5 Ge 5.5 Sn 0.5 O 26.25 ceramics, and the worst electrical conductivity among the examined systems appears in the La 9.5 Ge 5.5 Ga 0.5 O 26 ceramic. The La 9.5 Ge 5.5 Al 0.5 O 26 ceramic is accordingly selected for cell evaluation due to its ability to reach densification at 1,350 °C, its good electrical conductivity of 0.026 S cm –1 at 800 °C, and its acceptable thermal expansion coefficient of 10.1 × 10 –6 K –1 . The maximum power densities of the NiO‐SDC/La 9.5 Ge 5.5 Al 0.5 O 26 /LSCF‐SDC single cell are found to be respectively 0.22, 0.16, 0.11, and 0.07 W cm –2 at 950, 900, 850, and 800 °C.