Influence of yttria content on the preparation of nanocrystalline yttria-doped zirconia

Nanocrystalline zirconia doped with 0–10 mol % Y₂O₃ has been prepared by a combustion synthesis process, followed by a rapid densification process. The concentration of Y₂O₃ in the as-reacted zirconia appeared to have a significant influence on the reduction of the crystallite size, in the combustion temperature range studied (450 °C–550 °C), as well as on the stabilization of the tetragonal and/or cubic phases. The green compacts were densified by a fast-firing process. During fast-firing, the dwell temperature significantly affected the final average grain size and the final density of the article. On the other hand, the ranges of heating rates and dwell times that were used in this study were shown to have a much less significant effect on the article's final density and final average grain size. The yttria content had the largest influence on the final density and final average grain size. The densification took place much more rapidly in the 4 mol % Y₂O₃-ZrO₂ samples than in the 10 mol % Y₂O₃-ZrO₂ samples. In particular, the difference in densification rates between the samples with different Y₂O₃ content was attributed to the influence and magnitude of the associated grain-growth process. It was determined, however, that a high final density (>99% ρ_th) and a very fine final average grain size (<200 nm) could be simultaneously achieved with each of three different heating rates for the 4 mol% Y₂O₃-ZrO₂ articles.