Co-sintering of dense electrophoretically deposited LSGMC films on NiO-GDC anode for SOFC applications

Lanthanum gallate based perovskite oxides are primary candidates for electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). (La,Sr)(Ga,Mg,Co)O3 (LSGMC) is one of the most promising candidates for SOFCs due to its high oxygen ion conductivity at intermediate temperatures. Recently, a 1 kW SOFC operating at T < 800 °C using thick LSGMC as an electrolyte has been developed [1]. To further reduce the operating temperature of SOFCs we studied the electrophoretic deposition (EPD) of LSGMC thin films on a porous NiO-gadolinia doped ceria (GDC) supporting anode. The anode was prepared from commercial NiO-GDC powders, polyvinylidene fluoride (PVDF) and a nanometric carbon powder, dispersed in N-methyl-2 pyrrolidone. A green membrane was obtained after evaporation of the solvent, according to a procedure previously developed in our lab [2]. LSGMC powders were prepared by sol-gel and steric entrapment synthesis (SES). The sol-gel synthesis consists of complexing the cations by citrate. A gel was then obtained by polymerization of citrate [3]. In SES synthesis the gel was obtained by polymerization of polyvinyl alcohol, where the cations are entrapped. Fig. 1 shows XRD patterns of LSGMC powders prepared by SES method, calcined at 1450 °C for 12 hours. The LSGMC powders were then suspended in a solution of acetone and iodine and electrophoretically deposited on the green NiO-GDC membrane. A specifically developed thermal treatment allowed i) the removal of the organic binder in the membrane, ii) the combustion of the solid carbon with consequent gas development to preserve the porous structure of the anode, and iii) the densification of the electrolyte. In Fig. 2 the microstructure of the deposited LSGMC layer after 10 h sintering at 1350 °C is reported.