Interdiffusion between gadolinia doped ceria and yttria stabilized zirconia in solid oxide fuel cells: Experimental investigation and kinetic modeling

Abstract

Interdiffusion between the yttria stabilized zirconia (YSZ) electrolyte and the gadolinia doped ceria (CGO) barrier layer is one of the major causes to the increment of ohmic resistance 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 2 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 longterm operation at relatively lower temperature the impact of interdiffusion on cell degradation is negligible.

Computational engineering of the oxygen electrode-electrolyte interface in solid oxide fuel cells

“…2a, the distribution of Ce and Zr after the barrier layer sintering step at 1523 K for 2 h is presented, showing a ∼1-µm thick interdiffusion zone at the interface. We have previously reported a systematic investigation on the interdiffusion process between the YSZ electrolyte and the CGO barrier layer, including both experimental investigations and 1D kinetic modeling 33 . The detail will therefore not be repeated here.…”

“…% CeO 2 dissolved in the ZrO 2 part. The cubic ZrO 2 and CeO 2 phases can be thermodynamically treated as a single Cubic phase following our previous simulation result 33,34 . We then use SrO to represent the LSCF perovskite that provides Sr 2+ (or Sr) to react with ZrO 2 in IDZ.…”

“…The thermodynamic description of the ZrO 2 -CeO 2 -SrO system is listed in Table 1, where the sublattice model with charged species is adopted. The diffusion of Ce and Zr between CGO and YSZ can be treated as in our previous work 33,34 . On the other hand, the Sr migration through CGO layer is rather complex, and different mechanisms have been proposed in the literature, including gas-phase diffusion through the pore phase, surface diffusion, or bulk/grain boundary diffusion 40,41 .…”

“…Recently, the current authors have tried modeling the YSZ-CGO interdiffusion and thin layer SZO formation at the YSZ-CGO interface 33,34 . Several simplifications were made in the model, e.g., consideration of no CGO grain growth during high-temperature sintering and treating the SZO phase as a continuous layer instead of dispersed distribution.…”

Improved performance of a samarium-doped ceria interlayer of intermediate temperature solid oxide electrolysis cells by doping the transition metal oxide Fe2O3

“…By adding CuO in the GDC interlayer, the sintering temperature of the interlayer is reduced, so as to prevent the solid-state reaction between the interlayer and YSZ electrolyte. [16][17][18][19] In addition, cosintering can reduce the cost of the manufacturing process by reducing the necessary heat-treatment temperature, which is conducive to the commercialization of SOECs. It can be seen that improving the interlayer performance can enhance the performance of the oxygen electrode and the SOEC.…”