Increasing the thermal expansion of proton conducting Y-doped BaZrO3 by Sr and Ce substitution

Proton conducting oxide electrolytes find potential application in proton ceramic fuel cells and electrolyzers operating at intermediate temperatures, e.g. 400-600 degrees C. However, state-of-the-art proton conducting ceramics based on Y-doped BaZrO3 (BZY) have lower thermal expansion coefficient (TEC) than most commonly applied or conceived supporting electrode structures, making the assembly vulnerable to degradation due to cracks or spallation. We have increased the TEC of 20 mol% Y-doped BZY (BZY20) by partially substituting Ba and Zr with Sr and Ce, respectively, to levels which still maintain the cubic structure and sufficiently minor n-type conduction; (Ba0.85Sr0.15)(Zr0.7Ce0.1Y0.2)O-2.9 (BSZCY151020). High temperature XRD shows that this material has a cubic structure (space group Pm (3) over barm) in the temperature range of 25-1150 degrees C and a linear TEC of similar to 10 x 10(-6) K-1, as compared to the similar to 8 x 10(-6) K-1 for BZY. It exhibited a DC conductivity of similar to 5 mS cm(-1) at 600 degrees C in wet H-2. This electrolyte with increased TEC may find application in proton ceramic electrochemical cells in general and metal supported ones in particular.