Abstract :
We describe a defect and transport model
for acceptor doped La2 xSrxNiO4þd with the layered
K2NiF4 structure. The model includes mobile oxygen
interstitials in the rocksalt layers and oxygen vacancies
in the perovskite layers of the crystal structure. Based
on fits of literature data of the deviation from stoichiometry,
defect concentrations have been calculated for
La1.5Sr0.5NiO4+d as a function of p(O2) for 1,073–
1,223 K. Application of the transport model to oxygen
permeation data obtained in this work clearly indicates
that the oxygen transport in La1.5Sr0.5NiO4+d is primarily
governed by migration of mobile oxygen interstitials.
According to the model calculations, a
significant contribution of vacancy migration to the
oxygen permeation process is to be expected only for
oxygen partial pressures lower than 10–5 bar at 1,223 K
and even lower partial pressures at 1,073 and 1,173 K.
As yet, permeation data are not available for such low
partial pressures, which is why oxygen migration via
vacancies could neither be confirmed nor ruled out.
