Graded Ni–YSZ anode coatings for solid oxide fuel cell prepared by EB-PVD

Abstract

In order to reduce concentration polarisation from the solid oxide fuel cell (SOFC) anode and the internal stress originating from the thermal expansion mismatch between the anode and electrolyte, a NiO–YSZ coating with a graded composition distribution was prepared by electron beam physical vapour deposition (EB-PVD) through adjusting the electron beam currents. Then the graded Ni–YSZ coating was obtained after a reduction treatment from this NiO–YSZ coating. A graded distribution in contents of both nickel and zirconium was found in this Ni–YSZ coating from the electron probe microanalysis (EPMA) result. Scanning electron microscopy (SEM) observation exhibited a continuous variation in porosity and pore diameter along the direction across the coating thickness. In this coating, a high porosity of up to 43% and an average pore diameter of about 1 µm were obtained in the part close to the substrate, while a low porosity of 10% and mean pore diameters of about tens of nanometres were achieved in the part close to the coating surface. This pore structure not only could decrease the concentration polarisation, but also facilitate the following preparation of dense electrolyte films.