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

• Published in: Membranes (Basel) Vol. 9; no. 8; p. 95
• Main Authors: Han, Donglin, Kuno, Kenji, Uda, Tetsuya
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 02.08.2019; MDPI
• Subjects: Anodes; Barium oxides; barium zirconate; Barium zirconates; Cations; Composition; Control methods; Diffusion layers; Electrochemical analysis; Electrochemistry; Electrolysis; Electrolytes; Electrolytic cells; fuel cell; Fuel cells; High temperature; magnesia; Magnesium oxide; Methods; Morphology; Ni diffusion; Nickel oxides; proton conductor; Sintering; Solid solutions; Spectrum analysis; Substrates; Japan
• ISSN: 2077-0375; 2077-0375
• DOI: 10.3390/membranes9080095

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.