Towards high-strength electrolyte-supported solid oxide fuel cells

Abstract

The functionality and structural reliability of electrolyte-supported solid oxide fuel cells depend crucially upon the load-bearing capability of the ceramic electrolyte. In this work, the effect of thickness on the mechanical strength of tape-casted 8 mol% yttria-stabilized zirconia electrolyte discs was investigated. Samples with 98 % relative density and 2–3 µm grain size fabricated with thicknesses between 75 µm and 360 µm were mechanically tested using an adapted biaxial bending test. Thin electrolytes with biaxial strength up to 1 GPa could be produced. The measured characteristic strengths ranged from σ0 = 940 MPa to σ0 = 520 MPa for thin and thick samples, respectively, yielding a common Weibull modulus of m = 6. A higher strength scaled with decreasing thickness, confirming the “size effect” as in many technical ceramics. The measured ionic conductivity was above 0.1 S/cm at 1000 °C, which is in good agreement with commercial or conventionally prepared electrolytes.