RESUMO
Doped-BaCeO3 has high protonic conductivity at intermediate temperature, but poor chemical stability. In contrast, doped-BaZrO3 is rather stable, but has poor protonic conductivity. In this study, the BCY-BCZY bi-layer system was investigated in the hope of the synergetic improvement of high conductivity and good chemical stability. Nano-sized the BCY and modified-BCZY powders were prepared by the citric-nitrate route and bi-layer electrolyte made of BCY covered with a thin film BCY-BCZY deposited by the electrostatic slurry spray deposition. The improvement of chemical stability, measured in CO2 atmosphere, is turned out to be resulted from the substitution of Zr4+ cation. Overall, the BCY-BCZY bi-layer electrolyte shows promising improvement in chemical stability against produced water on the cathode side during the cell operation.
RESUMO
The samarium-doped barium cerate (BaCe0.8Sm0.2O(3-delta), BCS) nano crystalline powders were synthesized via citric-nitrate method. The BCS nanopowders were prepared with various molar ratio of citric acid to metal nitrate. The pure perovskite structure was obtained from the BCS calcinated at 1200 degrees C and its crystalline size was increased with increase of the molar ratio citric acid to metal nitrate, while the aggregated particle size was significantly decreased as increasing the molar ratio. Also, excellent densification behavior was observed when high molar ratio of citric acid to metal nitrate was used. It was clarified that the molar ratio of citric acid determines the aggregated particle size and, in turn, finial microstructure after sintering.
RESUMO
Despite of the highest proton conductivity, barium cerate electrolytes are well known for the deficiency of chemical stability at elevated temperature under CO2 atmosphere. This work is focused on improving chemical stability of lanthanum doped barium cerate (BCL) powder for electrolyte. Although lanthanum doping causes distortion of perovskite structure lattice, immoderate doping could stabilize structure due to increasing symmetry of structure lattices. The thermogravimetric analysis and AC impedance measurements revealed that the lanthanum doping suppresses the reaction between barium and carbonate and this effect results in sufficient improvement in ionic conductivity in operating temperatures range. It was confirmed that BaCe0.7La0.3O3-delta (BCL30) was the most stable composition and the conductivity of BCL30 is high as 3.8 S x cm(-1) x K at 700 degrees C.
RESUMO
Strontium-doped samarium cobaltite (Sm0.5Sr0.5CoO3-delta, SSC) fibers were successfully fabricated by electrospinning of a precursor gel derived from polyvinyl alcohol (PVA) and aqueous metal nitrate. After calcination of the as-spun SSC fibers in microwave furnace at above 500 degrees C, SSC fibers of 100 +/- 20 nm in diameter with well-developed cubic-perovskite structure were successfully obtained. The crystal structure morphology, and grain structure of the fibers were influenced by the calcination temperature and the grain structure was evolved to "bamboo" structured polycrystalline SSC at above 700 degrees C.
RESUMO
In this study, the dispersion stabilization characteristics of the poly(vinyl butyral) (PVB) adsorbed yttria-stabilized zirconia (YSZ) was investigated. The addition of PVB showed remarkable dispersion effect to the YSZ slurry prepared with isopropyl alcohol (IPA) and toluene as a bi-solvent system, PVB as a dispersant medium and YSZ powders. The agglomerated YSZ particle size decreased with PVB addition until 3 wt% and PVB added more than 3 wt% acted as a binder. The smallest particle size was obtained at 3 wt% PVB and the more PVB addition causes reflocculation of YSZ particles. The relative amount of adsorbed PVB onto the YSZ surface increased with increasing PVB contents. It turns out that the YSZ slurry dispersion stabilization was improved by the interaction between the hydroxyl group of YSZ surface and O-H group in PVB which is newly formed Zr-O-C bonding.
