Conductivity recovery by redox cycling of yttrium doped barium zirconate proton conductors and exsolution of Ni-based sintering additives


Owing to their high stability and good bulk proton conductivity yttrium doped barium zirconate-based materials are considered as potential electrolytes for protonic ceramic fuel cell applications. Nonetheless, their refractory nature leads to problematic densification that can necessitate the addition of sintering additives. While these additives assist processing, undesirable, strong, negative impacts on proton conductivity have been regularly reported. The current work assesses the potential sintering additives NiO, BaNiOx and BaY2NiO5 and their influence on subsequent electrochemical properties of BaZ-r(0.85)Y(0.15)O(3-delta). All sintering additives allow dense electrolyte materials (>95%) to be formed at temperatures below 1450 degrees C, with enhanced grain growth; with the largest grain growth being offered by the BaNiOx additive. Degradation in overall electrical performances is shown to be bulk related, corresponding to large reductions in bulk conductivity up to two orders of magnitude, whilst grain boundary conductivities are less affected. Most importantly, the current article demonstrates that these high depletions in bulk proton conductivity can be effectively inverted by redox cycling in relatively mild conditions (750 degrees C, cycling from N-2 to H-2 and back to N-2), opening the way to improve processing of these materials whilst maintaining high levels of proton conductivity. (C) 2016 Elsevier B.V. All rights reserved.



subject category

Chemistry; Electrochemistry; Energy & Fuels; Materials Science


Nasani, N; Pukazhselvan, D; Kovalevsky, AV; Shaula, AL; Fagg, DP

our authors


The authors gratefully acknowledge finding from the Fa, POPH, PTDC/CTM-EME/6319/2014, FCT Investigator Programme, projects IF/00280/2012/CP0172/CT0006, IF/01344/2014/CP1222/CT0001, IF/00302/2012 and UID/CTM/50011/2013, QREN, FEDER and COMPETE (Portugal) and the European Social Fund, European Union. Pukazh acknowledges FCT for the grant, SFRH/BPD/88756/2012.

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