The Microstructure of Ni-GDC anode functional layers (AFLs) for lower temperature solid oxide fuel cells (SOFCs) were investigated. AFLs with various Ni-GDC compositions (50-80 wt% NiO in AFL before reduction) were quantified by a 3D reconstruction technique using a focused ion beam (FIB)/scanning electron microscope (SEM) dual beam system. Each AFL sample was sectioned into 150 slices with 60 nm intervals. Amira software allowed for alignment, segmentation, and reconstruction of the 2D SEM images into a 3D image. From these reconstructions, volume fractions, effective particle size, phase gradient, and surface area for Ni, GDC, and pore phases were quantified. The estimated phase volume fraction was well matched with the theoretical value. The optimal effective particle size and highest surface area was observed at 49 vol% Ni AFL The active triple phase boundaries were calculated based on the connectivity of voxels for each phase. The highest TPB density was also achieved at 49 vol% Ni AFL which is a 1:1 volume ratio of Ni to GDC phase. The TPB density shows an inverse proportionality to the electrode ASR measured from SOFC operation. (C) 2012 Elsevier B.V. All rights reserved.