  Interdiffusion between the yttria stabilized zirconia (YSZ) electrolyte and
the gadolinia doped ceria (CGO) barrier layer is one of the major causes to the
degradation of solid oxide fuel cells (SOFCs). We present in this work
experimental investigations on CGO-YSZ bi-layer electrolyte sintered at 1250 C
or 1315 C and element transport as a function of sintering temperature and
dwelling time. In order to quantitatively simulate the experimental
observations, the CALPHAD-type thermodynamic assessment of the CGO-YSZ system
is performed by simplifying the system to a CeO2-ZrO2 quasi-binary system, and
the kinetic descriptions (atomic mobilities) are constructed based on critical
review of literature data. The CGO-YSZ interdiffusion is then modeled with the
DICTRA software and the simulation results are compared with the experimental
data under different sintering or long-term operating conditions. The
corresponding ohmic resistance of the bi-layer electrolyte is predicted based
on the simulated concentration profile. The results implies that the
interdiffusion across the CGO-YSZ interface happens mainly during sintering at
high temperature, while during long-term operation at relatively lower
temperature the impact of interdiffusion on cell degradation is negligible.
