Conductivity of yttria stabilized zirconia (YSZ) produced from weakly agglomerated nanopowder investigated by ac impedance spectroscopy. Dense ceramic samples with grain size from 90 to 800 nm were made by variation of both pressing and sintering conditions. It is found that the bulk conductivity is independent of grain size, but grain boundary conductivity is depended. Observed grain boundary resistance increases with grain size. It is in contradiction with previous results observed for range 1–18 μm where grain boundary resistance decreases with grain size.
