The effects of different processing steps and processing conditions for the fabrication of Y2O3 and Lu2O3 ceramics were investigated, particularly the effects of calcination, and sintering temperature on the content of open-volume and electronic defects. Ceramic bodies were prepared from calcined powders by sintering from 1400 degrees C to 1700 degrees C for 20 h. Density was determined by the Archimedes method and showed pellets reached about 99% of Y2O3 density for temperatures 1450 degrees C, and reached 98% for sintering at 1700 degrees C for Lu2O3. The content of open-volume defects was followed by positron annihilation lifetime (PAL) measurements. For both materials, two lifetimes were obtained. The faster lifetime, 211 ps for Y2O3 and 204 ps for Lu2O3, was assigned to bulk annihilation with possible contribution of grain boundaries. The longer lifetime was assigned to positronium annihilation in open-volume defects with radii of 2-4 angstrom. Doppler broadening analysis revealed the same type of defect in Lu2O3 ceramics for all sintering temperatures. PAL analysis results showed that densification was achieved through the elimination and agglomeration of open-volume defects. Thermoluminescence (TL) measurements of Y2O3 showed that sintering is beneficial in eliminating traps and/or recombination centers, and that higher sintering temperatures increase TL signal.