Mass transport in La2Ni1-xCoxO4+δ oxides with the K2NiF4 structure

Oxygen diffusion and surface exchange coefficients have been determined for the materials La2Ni1 - xCoxO4 + delta by the Isotope Exchange Depth Profile Secondary Ion Mass Spectrometry (IEDP SIMS) method. It is shown that the addition of cobalt (0 < x < 0.5) leads to the formation of single-phase materials and that the oxygen diffusion coefficient varies only slightly with x. In contrast, the surface exchange coefficient was found to be strongly dependent upon the value of x, with the activation enthalpy for this process dropping to values as low as - 20 kJ mol(-1) for the high cobalt content material. (C) 2002 Elsevier Science B.V. All rights reserved.