Surface Cation Segregation and Chromium Deposition on the Double-Perovskite Oxide PrBaCoO.

The surface chemistry and the Cr tolerance ability of oxygen electrodes play a vital role in the performance and long-term stability of solid oxide cells (SOCs). In this paper, the surface cation segregations on the double-perovskite oxide PrBaCoO (PBCO) and its relationship with Cr deposition are reported. During high-temperature annealing in an O atmosphere, the elements Ba and Co diffuse out of the lattice and form many BaO and CoO precipitates on the surface, mainly located at grain boundaries. In the presence of volatile Cr species, the observation of BaCrO, but not CoCrO, on a segregated PBCO surface reveals that the Cr deposition preferentially takes place on segregated BaO rather than on CoO precipitates. Our results show that segregated BaO precipitates are very active toward Cr vapor and PBCO is not a Cr-tolerant oxygen electrode for SOCs operating at high temperatures, despite its superior electrochemical performance.