Preparation of dense ThO2-based ceramics by Sc doping and simple sintering method

The Th1-xScxO2-x/2 (0 ≤ x ≤ 0.1) ceramic system with high density was originally prepared via a co-precipitation route and simple sintering method. XRD analysis indicates that the Th1-xScxO2-x/2 ceramics exhibited a single cubic fluorite structure and a slight increase of cell parameters. SEM images show that Sc doping contributed a decreasing pores and more uniform grain distribution. The calculated relative densities could reach up to a value higher than 99.0% for x = 0.01 during the isothermal process while the maximum actual relative density was only about 77.4% during the non-isothermal sintering process. And the analysis of grain growth kinetics demonstrates that Th1-xScxO2-x/2 was a solid solution with a high solubility of Sc for x = 0.01 and a low solubility of Sc for both x = 0.05 and x = 0.1, which resulted in a strongly slow grain growth for x = 0.1 due to the solute drag effect. The sintering mechanism investigation also illustrates that low amount (x = 0.01) of Sc doping could significantly enhance the densification sintering of ThO2-based ceramics and reduce the sintering temperature by nearly 150 °C. Such strategy has issued the bottleneck problem existed in the densification sintering of ThO2-based ceramics at a lower temperature without any other special sintering atmosphere, which even could be applicable for other ceramics difficult to sinter.