Effect of CO 2 Exposure on the Chemical Stability and Mechanical Properties of BaZrO 3 ‐Ceramics

The reactivity of BaZrO 3 with CO 2 has been addressed as one of the major challenges with BaZrO 3 ‐based electrolytes in protonic ceramic fuel cells. Here, we present a study of the effect of CO 2 exposure on BaZrO 3 ‐materials at elevated temperatures. Dense BaZr 1− x Y x O 3− x /2 ( x = 0, 0.05, 0.1, 0.2) and BaCe 0.2 Zr 0.7 Y 0.1 O 2.95 ceramics were prepared by sintering of powder prepared by spray pyrolysis. The Vickers indentation method was used to determine the hardness and estimate the fracture toughness of pristine materials as well as the corresponding materials exposed to CO 2 . Formation of Ba CO 3 on the surface of exposed ceramics was confirmed by X‐ray diffraction and electron microcopy. The reaction resulted in formation of Ba‐deficient perovskite at the exposed surface. The reaction with CO 2 was most pronounced at 650°C compared to the other temperatures applied in the study. The reactivity was also shown to depend on the Y‐content and the grain size and was most pronounced for BaZr 0.9 Y 0.1 O 2.95 . The reaction with CO 2 was observed to have a profound effect on the fracture toughness of the ceramics, demonstrating a depression of the mechanical stability of the materials. The results are discussed with respect to the chemical and mechanical stability of BaZrO 3 materials, with particular emphasis on the composition and grain size.