ThO 2- n mol% Y 2O 3 ceramic powders with submicron average particle size were prepared by the citrate technique using thorium oxalate, yttrium nitrate, citric acid and ethylene glycol. For n=3, 6, 9 and 12, reactive thoria-yttria solid solution powders with surface areas of 17.3, 11.1, 9.4 and 8.7 m 2/g, respectively, were obtained. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were carried out for characterization of the powders. Pressing and sintering at 1550 °C/2 h produced pellets with densities higher than 90% of the theoretical density. The pellets were also characterized by XRD and SEM.