Gas-Tight and Crystalline CGO Electrolytes for SOFC Deposited by Spray Pyrolysis

Gadolinea-doped ceria (CGO) has a quite high ionic conductivity at 600-650°C and it is being of great interest as an electrolyte for SOFC to operate at intermediate temperatures. This material has higher ionic conductivity when it is compared to yttria-stabilized zirconia; another way to increase ionic conductivity is to decrease the thickness of the electrolyte. To reach this goal spray pyrolysis technique is one of the most promising processing methods for production of thin layered solid oxide fuel cells at intermediate temperature because of the cost-effective and non-necessity of post-heat treatment at high temperature compared with others electrolyte formation processes. This technique consists to spray a precursor solution on a heated substrate. Controlling the parameters is possible to obtain both porosity (suitable for electrodes) and dense morphology (suitable for electrolytes). The aim of this study was to achieve good quality coatings, with which may be used as SOFC electrolyte and to test its performance in a SOFC. Gadolina-doped ceria (Ce0.8Gd0.2O1.9-ɣ) was deposited by spray pyrolysis on NiO-YSZ porous substrate. The films obtained were crystalline without a post-heat treatment, gas-tight, dense, crack-free, and with some particles aggregated. The performance of this film as a SOFC electrolyte was tested. The results show that a thin electrolyte (< 5µm) has a lot of electronic conductivity decreasing the maximum output power density reached and the cathode adherence is critical in its performance.