Fracture strength and Weibull analysis of Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxygen transport membranes evaluated by biaxial and uniaxial bending tests

The present study evaluates the fracture strengths and the Weibull modulus of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) oxygen transport membranes by means of biaxial and uniaxial bending tests at both room temperature (RT) and 800 °C. The fracture strengths obtained from the biaxial bending tests are much lower than those obtained from the uniaxial bending tests while Weibull moduli (m) are similar. By utilising Weibull statistics the uniaxial strengths can be predicted from the biaxial values at both RT and 800 °C. Fracture surfaces at both RT and 800 °C show only a transgranular fracture mode. Failure origins are also determined by scanning electron microscope (SEM) based on the fractographic principles. Most defects determining the fracture strength of this particular material are found to be pores with a relatively large size.