The structure of porous yttria-stabilized zirconia (YSZ) has been modified by infiltration with concentrated hydrofluoric acid for application in solid-oxide fuel cell electrodes. Dissolution and precipitation of the YSZ greatly increased the surface area of the porous YSZ and formed sheets and pillars of YSZ within the structure that were largely stable to calcination at 1373 K. Electrodes made by infiltration of 35 wt% ( 20 vol%) La(0.8)Sr(0.2) FeO(3) into the pore structure exhibited significantly lower impedances at 973 K, even after calcination to 1373 K.