Comparison of methodologies for determination of fracture strength of 8 mol % yttria-stabilized zirconia electrolyte materials

The widely used yttria-stabilized zirconia (YSZ) electrolyte is subjected to thermal and external stresses under operation, so that the enhancement of the mechanical properties is an important issue in planar solid oxide fuel cells. Fracture strengths of 8 mol % YSZ electrolytes as 100 X 100 mm squire plates, 23 mm disks, and 17 mm disks were evaluated using plate tensile, ball-on-ring, and pressure-on-ring testing methodologies, respectively. Finite element analysis (FEA) was validated and used to calculate the stress distribution and peak stress for the biaxial strength tests. A Weibull analysis was carried out on the test/FEA-predicted peak stresses, and Weibull strength, modulus, and material scale parameters were found for each test methodology. The methodologies were compared and evaluated based on the results of the Weibull analysis; the pressure-on-ring test is preferred for brittle thin-film fracture strength testing.