Influence of Processing Conditions on the Microstructure and Mechanical Properties of Sintered Yttrium Oxides

High-purity (99.9%) yttrium oxide (Y{sub 2}O{sub 3}) powder has been consolidated, either by vacuum sintering (VS) or by hot pressing (HIP). As the dense polycrystalline ceramics contained point defects, mainly oxygen vacancies, oxidation treatment was applied at 1,500 C for 2 h. The two materials were compared with respect to mechanical, elastic, and thermal properties, and this work demonstrated that the HIPed oxide had the best performance. The beneficial effect of the HIP technique was mainly due to the achievement of a slightly higher densification at a much lower applied temperature. This technique prevented any grain coarsening and allowed them to obtain a more homogeneous structure. 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.