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Focused ion beam (FIB) – scanning electron microscopy (SEM) allowed the characterization of the microstructure of two solid oxide fuel cells prepared at different sintering temperatures. 3D volume reconstruction showed that a relatively low sintering temperature significantly and positively affected distribution, volume and particle size of yttria-stabilized zirconia, nickel, and pore phases inside the anode, as well as the extent of the important triple-phase boundary interface. The poor performance of the T1 sample sintered at a higher temperature is explained by the poorly connected pore network and very low-density triple-phase boundary. The pore space inside the T1 anode was unable to ensure continuous hydrogen flow from the inlet to the outlet and thus exhibited very low gas permeability. In contrast, the T2 sample sintered at a lower temperature had approximately equal amounts of YSZ and nickel and larger pores, which allowed formation of significantly more TPB electrochemical reaction sites. The higher power density of the T2 cell was also the result of its robust pore network capable of transporting hydrogen throughout the anode. The methodology used in this paper eliminates the need for employing hypothetical structures and provides accurate estimates of the investigated parameters by evaluating microstructures that were successfully reconstructed using high-resolution microscopy techniques.