A Study of 8YSZ/GDC Bi-Layered Electrolyte: The Effect of 2 Mol% Fe2O3 Dopant on Sintering and Conductivity

Thursday, 30 July 2015
Hall 2 (Scottish Exhibition and Conference Centre)
A. S. Mehranjani (The University of Sheffield), D. J. Cumming, A. V. Call, and R. H. Elder (University of Sheffield)
The primary requirements for an electrolyte material in a Solid Oxide Cell (SOC) is the ability to provide a sufficiently high level of oxide ion conduction while preventing both the mixing of reactant gas species and leakage of current through the electrolyte. Commonly, 8 mol% Yttria-stabilised Zirconia (8YSZ) or Gd0.1Ce0.9O1.95 (GDC) are used in high performance cells. Whilst GDC has higher oxide ion conductivity than YSZ, it suffers from electronic conduction due to the partial reduction of Ce4+ to Ce3+ during operation which is detrimental to cell performance. In this work we present the use of a bi-layer 8YSZ/GDC electrolyte as an effective solution to avoid ceria reduction in a fuel (reducing) environment, thereby preventing current leakage across the electrolyte, while maintaining high oxide ion conduction.  Electrolytes were produced via tape-casting, a low-cost, mass-production technique.  A transition metal oxide sintering aid of 2 mol% Fe2O3 was used to reduce the sintering temperature while also mitigating the formation of a low conductivity interlayer. This study aims to determine the role of Fe2O3 during the sintering process and its subsequent influence on microstructure and the total conductivity of the bi-layer electrolyte.