Densificação de BaZr0,1Ce0,7Y0,1Yb0,1O3-γ para aplicação como eletrólito de Células a Combustível de Óxido Sólido
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2015
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SIMPÓSIO BRASILEIRO DE ELETROQUÍMICA E ELETROANALÍTICA, 20.
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Resumo
BaCeMIIIO3-δ (MIII = metals with valence 3+ as Y, Yb, Gd, etc) is the most investigated
proton conductive ceramic to be applied as electrolyte in the electrochemical devices as Solid Oxide Fuel
Cell (SOFC). Despite their high conductivity, the low chemical stability in the presence of acidic gases (CO2
and SO2) requires improvements. The stability can be provided by doping with zirconium [1] and the loss in
conductivity due to the presence of zirconium can be retrieved by adding yttrium and ytterbium [2]. The
conductivity at the grain interface is also a major factor for an efficient electrolyte, so the synthesis is an
important step. One of the synthesis methods used to obtain complex stoichiometry materials is Pechini and
their variations as EDTA-Citrate method [3]. However, this class of methods have still hurdles to obtain
dense materials due to the difficulty to eliminate carbonates. One way to facilitate the elimination of
carbonates is to obtain materials with high surface area. The aim of this work is to synthesize
BaZr0,1Ce0,7Y0,1Yb0,1O3-δ by citrate-EDTA method and evaluate the influence of pH (~5 and ~8) during the
precursor synthesis in order to obtain materials with high surface area. After synthesizing the resins, they
were heat treated at: 600ºC/4h and 1000ºC/3h (all in air). The obtained ceramic powders were characterized
by TG/DTA, XRD, EDX, FTIR and N2 adsorption at 77K. After, the green ceramic pellets were obtained, they
were submitted to the following sintering process: 500ºC/1h, 1000ºC/1h and 1450ºC/3h (all in air). The dense
pellets were characterized by XRD, EDX, relative density by Archimedes method, SEM and impedance
measurement. Regarding to the powder samples, the TG/DTA results indicated the formation of perovskite
phase at the range of 700ºC-1000ºC (endothermic process) and, at same time the carbonate is eliminated
(exothermic process). The XRD patterns of materials calcined at 1000ºC/3h showed that EDTA-citrate
method provided materials under perovskite type structure when synthesized in boths pHs. The analysis by
EDX (materiais obtained in boths pHs and calcined at 1000ºC/3h) confirmed that the compositions are close
to the nominal one. The FTIR results indicated the carbonates are still present even calcining at 1000°C/3h,
for boths pHs. The N2 adsorption results showed that the materials synthesized in pH~8 exhibited higher
surface area than materials synthesized in pH~5 (22 m2/g and 9 m2/g, respectively, for materials calcined at
600ºC/4h). Regarding to the dense materials, the XRD patterns of the pellets synthesized by controlling
pH~8 and sintered at 1450ºC/3h showed crystalline structure with higher symmetry (orthorhombic phase)
while the XRD patterns of the pellets synthesized at pH~5 showed phase with lower symmetry (monoclinic
phase). The analysis by EDX in the samples sintered at 1450ºC/3h confirmed that the composition is close to
the nominal one, for boths pHs. The pellets obtained from materials synthetized at pH~8 showed higher
relative density than the pellets at pH~5, being 98% and 94%, respectively. The SEM analysis corroborated
these results. The impedance spectroscopy showed the total conductivity within the densified material (pH 8)
is in the range 11-0,54 mS/cm when measured in wet air at the temperature of 800ºC-400ºC. In other words,
considering a current density of 300mA/cm2 and a thickness of 20 m, the overpotential is close to 100 mV
at 700oC, showing that the materials prepared by EDTA-citrate method can be used as electrolyte in the
intermediate temperature SOFC (IT-SOFC).
Como referenciar
SILVA, R.I.V. da; YOSHITO, W.K.; MARTINS, M.L.; ICHIKAWA, R.U.; SANTOS, D.I. dos; MARTINEZ, L.G.; SAEKI, M.J. Densificação de BaZr0,1Ce0,7Y0,1Yb0,1O3-γ para aplicação como eletrólito de Células a Combustível de Óxido Sólido. In: SIMPÓSIO BRASILEIRO DE ELETROQUÍMICA E ELETROANALÍTICA, 20., 17-21 de agosto, 2015, Uberlândia, MG. Resumo... Disponível em: http://repositorio.ipen.br/handle/123456789/27419. Acesso em: 22 Feb 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.