Studies on Conductivity of Composite GdCeO2-Carbonate Electrolytes for Low Temperature Solid Oxide Fuel Cells

Abstract

The current state-of-the-art in using electrolyte, yttria stabilized zirconia (YSZ) in solid oxide fuel cell suffers from a variety of challenges for commercialization due to the unavailability of sealant materials and corrosion at high temperature (∼800°C). Recently, development of CeO2-carbonate based low temperature solid oxide fuel cells capable of operating at 300–600°C attracted the attention of many researchers. Three compositions have been prepared for this study: 1) GdCeO2-(LiNa)CO3, 2) GdCeO2-Li2CO3 and 3) GdCeO2-Na2CO3. Phase formation, microstructural evolution and ionic conductivity have been investigated. XRD results indicated the formation of GdCeO2-(LiNa)2CO3 phase. However, the peaks corresponding to carbonate phase was absent in the case of GdCeO2-Li2CO3 and GdCeO2-Na2CO3. SEM microstructure analysis revealed enhanced crystal growth in the case of GdCeO2-Na2CO3. The sample Gd-CeO2 that contains 25wt.% (LiNa)CO3 sintered at 600°C showed the highest ionic conductivity of 0.1600 Scm−1 at 550°C and low activation energy of 0.0912 eV. The ionic conductivities of GdCeO2-Li2CO3 and GdCeO2-Na2CO3 were 0.0050 and 0.0549 Scm−1 respectively at 550°C. The highest ionic conductivity of GdCeO2-(LiNa)2CO3 is attributed to higher defect density formed by the eutectic composition of Li2CO3 and Na2CO3 ∼497°C.