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Open AccessArticle

Correlation between Concentrations of Ni and Y in Y-Doped BaZrO3 Electrolyte in Co-Sintered Cells: A Case of Controlled NiO Activity by Using MgO-NiO Solid Solution as Anode Substrate

Department of Materials Science and Engineering, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Japan
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Membranes 2019, 9(8), 95; https://doi.org/10.3390/membranes9080095
Received: 16 July 2019 / Revised: 29 July 2019 / Accepted: 30 July 2019 / Published: 2 August 2019
(This article belongs to the Special Issue Ceramic Membranes for Fuel Cell Applications and Hydrogen Production )
BaZr0.8Y0.2O3-δ (BZY20) is promising to be applied as an electrolyte in fuel cells, electrolysis cells, etc. However, when a half cell composed of a BZY20 electrolyte layer and a BZY20-NiO composite anode substrate is co-sintered (1400–1600 °C), Ni diffuses from the anode substrate into the electrolyte layer. Y content in the electrolyte layer decreases dramatically, since BZY20 cannot be equilibrated with NiO at such high temperature. Such Ni diffusion and Y loss are detrimental to the electrochemical performance of the electrolyte layer. In this work, we added MgO-NiO solid solution into the anode substrate to adjust the NiO activity (aNiO) during the co-sintering process, and used three different co-sintering methods to control the BaO activity (aBaO). The results revealed that by decreasing aNiO in the system, the as-co-sintered electrolyte layer had the composition shifting towards the direction of high Y and low Ni cation ratios. A clear correlation between the intra-grain concentration of Ni and Y was confirmed. In other words, to prepare the electrolyte with the same Y cation ratio, the Ni diffusion into the electrolyte layer can be suppressed by using the MgO-NiO solid solution with a high MgO ratio and a low Ni ratio. Moreover, by increasing aBaO, we found that the Y cation ratio increased and approached the nominal value of the pristine BZY20, when Mg1−xNixO (x = 0.3 and 0.5) was used. In summary, both aNiO and aBaO play important roles in governing the composition of the electrolyte layer prepared by the co-sintering process. To evaluate the quality of the electrolyte layer, both the intra-grain Y and Ni concentrations should be carefully checked. View Full-Text
Keywords: proton conductor; barium zirconate; fuel cell; Ni diffusion; magnesia proton conductor; barium zirconate; fuel cell; Ni diffusion; magnesia
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Han, D.; Kuno, K.; Uda, T. Correlation between Concentrations of Ni and Y in Y-Doped BaZrO3 Electrolyte in Co-Sintered Cells: A Case of Controlled NiO Activity by Using MgO-NiO Solid Solution as Anode Substrate. Membranes 2019, 9, 95.

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