p-Type electronic conductivity, oxygen permeability and stability of La2Ni0.9Co0.1O4+δ†
Abstract
The oxygen permeability, total conductivity and Seebeck coefficient of La2Ni0.9Co0.1O4+δ were studied in the oxygen partial pressure range of 10−16 Pa to 50 kPa at 973–1223 K. The conductivity of La2Ni0.9Co0.1O4+δ is predominantly p-type electronic within the whole p(O2) range in which the K2NiF4-type structure exists. Thermally-activated mobility, the values of which are 0.02–0.08 cm2 V−1 s−1, and the p(O2) dependencies of electron-hole transport suggest a small-polaron conduction mechanism. Oxygen permeability of dense La2Ni0.9Co0.1O4+δ membranes, with an apparent activation energy of 192 kJ mol−1 in oxidising conditions, is limited by both bulk ionic conductivity and the surface exchange rate. The role of surface processes in limiting permeation is also significant under air/H2–