Structure and conductivity of praseodymium and yttrium co-doped barium cerates

Praseodymium-doped yttrium barium cerates were synthesised by solid-state reactions followed by quick sintering at 1500 °C for only 1 h achieving relative density > 96%. All studied compounds are stable in ambient air and reducing atmosphere (both wet and dry 5% H₂-Ar). The Zr-free sample (BaCe_0.7Y_0.2Pr_0.1O_3-δ) exhibits the highest conductivity of 0.0121 S cm^-1 at 700°C in air, comparable to results obtained for yttrium-doped barium cerate under similar conditions (0.014 S cm^-1). Pr-doped compounds were also found to retain much larger amounts of water as suggested by the higher conductivities obtained in wet hydrogen comparing to the values in ambient air. This latter phenomenon is of special interest as it suggests the possibility of higher ionic conductivities in water-containing atmosphere. On the other hand, co-doping of praseodymium and bismuth did not yield the expected enhanced electrical properties from the bismuth addition probably due to structural factors influenced by the diminution of the cerium content.