INFLUENCE OF PROCESSING CONDITIONS ON THE MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF SINTERED YTTRIUM OXIDES

High-purity (99.9%) yttrium oxide (Y2O3) powder has been consolidated, either by vacuum sintering (VS) or by hot isostatic pressing (HIP). A s the dense polycrystalline ceramics contained point defects, mainly o xygen vacancies, oxidation treatment was applied at 1500 degrees C for 2 h. The two materials were compared with respect to mechanical, elas tic, and thermal properties, and this work demonstrated that the HIPed oxide had the best performance. The beneficial effect of the HIP tech nique was mainly due to the achievement of a slightly higher densifica tion at a much lower applied temperature. This technique prevented any grain coarsening and allowed us to obtain a more homogeneous structur e. Consequently, improvements in microhardness, flexural strength, and thermal shock parameters were significant. Nevertheless, the elastic parameters and the toughness values of the two grades were very close to each other.