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

TL;DR

This study investigates the interdiffusion between CGO and YSZ in SOFCs through experiments and kinetic modeling, revealing that high-temperature sintering causes significant interdiffusion, but long-term operation at lower temperatures has minimal impact on degradation.

Contribution

It combines experimental analysis with thermodynamic and kinetic modeling to understand interdiffusion in CGO-YSZ bi-layer electrolytes in SOFCs, providing insights into degradation mechanisms.

Findings

Interdiffusion mainly occurs during high-temperature sintering.

Long-term operation at lower temperatures has negligible impact.

Simulation results align with experimental data.

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 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.