Yuria-doped zirconia compacts (2.5 mol%) of spray-pyrolysed powders were prepared by two routes: cold isostatic pressing (CIP) and explosive isodynamic compaction (EXIC). Starting powders of 6 nm mean primary crystallite size are tetragonal single-phased with good homogeneity in chemical composition and with a narrow crystallite size distribution. This paper reports on a comparative study of the microstructure of these pellets in terms of grain size and density. CIP and sintering at 1500 degreesC led to nanocrystalline ceramics consisting of an average primary grain size of 60 ran and characterized by a density of 96% of the theoretical value with an unimodal distribution of 300 nm average aggregate size. Ceramics with 6 nm average grain size were successfully obtained by EXIC but with densities as low as 65% of the theoretical one. Both ceramics were still tetragonal single-phased, characterized by a good purity: only 0.1 wt.% Si and some traces of Hf.