Phase stability and conductivity of Ba sub(1-y)Sr sub(y)Ce sub(1-x)Y sub(x)O sub(3-d) solid oxide fuel cell electrolyte

The structure, phase stability, and electrical properties of BaCe sub(1-x)Y sub(x)O sub(3- ) (x = 0-0.4) in humidity air and CO sub(2) atmosphere are investigated. XRD results indicate that the BaCe sub(0.9)Y sub(0.1)O sub(3-d) sample has a symmetric cubic structure, and its phase changes to tetragonal as the Y super(3+) doping amount increases to 20 mol%. The conductivity of BaCe sub(1-x)Y sub(x)O sub(3-d) increases with temperature, and it depends on the amount of yttrium doping and the atmosphere. BaCe sub(0.8)Y sub(0.2)O sub(3-d) exhibits the highest conductivity of 0.026 S cm super(-1) at 750 C. The activation energy for conductivity depends on yttrium doping amount and temperature. The conductivity of BaCe sub(0.8)Y sub(0.2)O sub(3-d) is 0.025 S cm super(-1) in CO sub(2) atmosphere at 750 C which is 3.8% lower than that in air due to reactions with CO sub(2) and BaCO sub(3) and the CeO sub(2) impure phases formed. The structure of BaCe sub(0.8)Y sub(0.2)O sub(3-d) is unstable in water and decomposes to Ba(OH) sub(2) and CeO sub(2) phases. It is found that the activation energy of samples in CO sub(2) atmosphere is higher than that of sample in air. Sr-doped Ba sub(1-y)Sr sub(y)Ce sub(0.8)Y sub(0.2)O sub(3-d) (y = 0-0.2) is prepared to improve the phase stability of BaCe sub(0.8)Y sub(0.2)O sub(3-d) in water. The conductivity of Ba sub(0.9)Sr sub(0.1)Ce sub(0.8)Y sub(0.2)O sub(3-d) is 0.023 S cm super(-1) at 750 C which was 11% lower than that of BaCe sub(0.8)Y sub(0.2)O sub(3-d), however, the phase stability of Ba sub(0.9)Sr sub(0.1)Ce sub(0.8)Y sub(0.2)O sub(3-d) is much better than that of BaCe sub(0.8)Y sub(0.2)O sub(3-d) in water.