BaCe_0.85-xZr_xSm_0.15O_3-δ(0.01 < x < 0.3) (BCZS): Effect of Zr Content in BCZS on Chemical Stability in CO₂and H₂O Vapor, and Proton Conductivity

In this paper, we report the chemical stability of a highly proton conducting Sm+Zr–codoped BaCe 0.85-x Zr x Sm 0.15 O 3-δ (BCZS) (0.01 < x < 0.3) in H 2 O vapor and CO 2 , and their electrical conductivity in air, N 2 + 3% H 2 O, H 2 + 3% H 2 O and N 2 + 3% D 2 O. All the prepared BCZS was found to be structurally stable against reaction with pure CO 2 at 400°C for 24 h, showing a positive role of Zr in providing chemical stability. However, at 600°C for 24 h, BCZS (0 < x < 0.2) showed the formation of BaCO 3 , while x = 0.3 remained stable at 20% CO 2 in N 2 . Upon exposure to H 2 O vapor at 90°C, Ba(OH) 2 .xH 2 O formation was observed for all the investigated BCZS whereas at 600°C all were found to be chemically stable. A maximum conductivity of 5 × 10 −3 Scm −1 is obtained for x = 0.3 member, which is about 40% of its Zr-free parent compound BaCe 0.85 Sm 0.15 O 3-δ (BCS). Current work shows that despite the drop in conductivity, Zr doping in BCS provides stability under pure CO 2 , especially considering the goal of decreasing operating temperature of solid oxide fuel cells (SOFCs) below 500°C.