Ionic conductivity of gadolinium-doped barium praseodymium oxide

To clarify the ionic conduction of Ba(Pr0.6Gd0.4)O3-alpha, the electrical c onductivity was measured in moist air and hydrogen atmospheres. The ionic t ransport number was estimated by a steam concentration cell, a hydrogen per meation cell, and a fuel cell. Temperature dependence of the conductivity i n a moist air atmosphere differed from that in a moist H-2 atmosphere. The conductivity under reducing conditions increases with time according to the crystal structure change of Ba(Pr0.6Gd0.4)O3-alpha due to oxygen loss in t he lattice site. Under moist air conditions, the dominant conduction specie s in the Ba(Pr0.6Gd0.4)O3-alpha electrolyte were mainly holes. However, the species changed into proton, oxide ion and hole by means of structure chan ge in a reducing atmosphere. It was considered that the ionic conduction oc curred due to the crystal structure change. It was predicted that this pecu liarity of the conductivity of barium praseodymium oxide influenced the non stoichiometric behaviour of Pr in the crystal structure. (C) 1999 Elsevier Science B.V. All rights reserved.