Gadolinia-doped ceria mixed with alkali carbonates for solid oxide fuel cell applications: I. A thermal, structural and morphological insight

Gadolinia-doped ceria mixed with alkali carbonates for SOFC applications: II – An electrochemical insight

“…The activation energy in this high-temperature domain, of about 0.25 eV, is close to that of pure Li 2 CO 3 -K 2 CO 3 (62-38 mol%) [43]. In a previous paper, we have shown the influence of the proportion of carbonates in the composite [40]. Conductivities of the GDC/LiK composite with three compositions: 80/20, 70/30 and 60/40 wt%, have been compared.…”

“…The Arrhenius conductivity diagram of the composite can be separated in a low temperature and a high-temperature region, separated by a discontinuity. At temperatures lower than the melting point of the mixed carbonate (T m < 488 C), also determined by differential thermal analysis (DTA) in a previous paper [40], the total conductivity of the GDCcarbonate composite is relatively close to the bulk i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 1 9 3 7 1 e1 9 3 7 9 conductivity of pure GDC. However, the difference between both conductivities tends to increase when lowering the temperature.…”

“…Thorough TGA and DTA analyses coupled to mass spectrometry have been developed by us in a previous paper [40]. Our purpose here is to analyze specifically the effect of cycling on the GDC/LiK20 composite by differential and thermogravimetric thermal analyses.…”

“…The DTA curves relative to the two cycles are perfectly superimposed, revealing an intense peak at 484 C, in agreement with the melting point of the Li 2 CO 3 -K 2 CO 3 (62-38 mol%) eutectic (488 C). When cooling, two exothermic peaks are observed, at 537 C and 444 C, they correspond to the beginning of Li 2 CO 3 crystallization and to the end of the eutectic formation (further details can be found in [40]). It was also previously demonstrated that after ageing during 168 h at 500 C under air, the shape of the TGA and DTA curves is almost the same than before ageing [40].…”

“…Doped ceria oxides have been tested with different molten salts (fluorides, sulphates, chlorides), but the most interesting are surely the carbonates [14e40]. A thorough analysis of the literature on such composites has been developed by us in a recent paper [40].…”