Microstructural characterization of SOFCNi-YSZ anode composites by low-voltage scanning electron microscopy

A lack of contrast between nickel and yttria stabilized zirconia (YSZ) in scanning electron microscopy (SEM) has long been an obstacle for complete microstructural characterization of porous Ni-YSZ anodes for solid oxide fuel cells (SOFC). In this paper a technique to achieve contrast between Ni and YSZ is described. The technique is based on imaging of a non-coated sample surface with an ordinary lateral secondary electron detector at a low voltage in a field emission (FE) SEM. A technique to visualize the degree of percolation of the electrically conducting phase (Ni) by low-voltage SEM is also developed. For this purpose the FE-SEM and an inlens secondary detector is utilized and applied to the same type of samples as above. A combination of these two techniques offers the possibility to fully characterize the microstructure of the Ni-YSZ anode, providing parameters such as size and distribution of all four components (percolating Ni, non-percolating Ni, YSZ and pores). (C) 2008 Elsevier B.V. All rights reserved.