Powders of BaYxCe1-xO3-delta (x=0, 0.1 and 0.15) with specific surface area of 6-8 m(2)g(-1) (BET equivalent particle size of 130-160 nm) were prepared by a modified solid-state route using nanocrystalline BaCO3 and CeO2 raw materials. These powders showed excellent densification at relatively low temperatures. Dense (96-97% relative density) ceramics with submicron grain size (0-4-0.6 mu m) were obtained after sintering at 1250-1280 degrees C. Ceramics sintered at 1450 degrees C revealed only a moderate grain growth (grain size <= 2 mu m), uniform microstructure and very high density (>= 98%). The total conductivity of the submicron ceramics at 600 degrees C was comparable with the reference values reported in the literature, meaning that the high number of grain boundaries was not a limiting factor. On lowering temperature, the contribution of the blocking grain boundaries becomes progressively more important and the conductivity decreases in comparison to coarse-grained ceramics. Microscopic conductivities of grain interior and grain boundary are the same irrespective of grain size meaning that the different macroscopic behaviour is only determined by a geometric factor (a trivial size effect). (C) 2008 Elsevier B.V. All rights reserved.