Strength and Toughness of Tape‐Cast Yttria‐Stabilized Zirconia

The biaxial flexural strength and fracture toughness of tape‐cast yttria‐stabilized zirconia, for application as the electrolyte in solid oxide fuel cells, have been measured at room temperature and at a typical operating temperature of 900°C. The flexural strength was measured in ring‐on‐ring loading and decreased from 416 MPa at room temperature to 265 MPa at 900°C. The fracture toughness was measured using two different techniques: indentation fracture and double‐torsion loading. The latter was more reliable and gave a fracture toughness of 1.61 ± 0.12 MPa·m 1/2 at room temperature and 1.02 ± 0.05 MPa·m 1/2 at 900°C. The flexural strength and fracture toughness were quantitatively consistent with fracture being initiated at the observed surface defects. The lower fracture toughness at 900°C is partly due to a reduction in elastic modulus and partly due to a reduction in the work of fracture.