Ultrafast High-Temperature sintering (UHS) was proposed in 2020 by Hu et al[i]. More detailed studies and characterization of the technique have been conducted since then, allowing better-controlled sintering to be completed[ii]. By comparing with conventional sintering, like other rapid heating methods, UHS showed an increased densification rate, but the detailed mechanism of the acceleration remains to be understood.
This research investigates the UHS densification behavior of α-alumina by comparing it with conventional sintering. As Al2O3 and Cr2O3 form a solid solution system, introducing Cr2O3 as a chemical tracer, its presence allowed the comparison of diffusion behavior. The small amount of Cr2O3 being doped does not affect the overall densification process and the green bodies can be densified up to 99.8% dense using UHS from room temperature to 1800K in 30 seconds. The density and microstructure are characterized. The concentration of Cr ions is plotted as a function of sintering temperature and time, and diffusivities are calculated. Comparison with conventional sintering showed a different Cr distribution in UHS, suggesting a different densification mechanism or diffusion pathway may be present during the sintering process. Possible explanations are discussed.

[i] Wang, Chengwei, Weiwei Ping, Qiang Bai, Huachen Cui, Ryan Hensleigh, Ruiliu Wang, Alexandra H. Brozena, et al. “A General Method to Synthesize and Sinter Bulk Ceramics in Seconds.” Science 368, no. 6490 (2020): 521–26. https://doi.org/10.1126/science.aaz7681.
[ii] Mishra, Tarini Prasad, Shufan Wang, Christian Lenser, Dylan Jennings, Moritz Kindelmann, Wolfgang Rheinheimer, Christoph Broeckmann, Martin Bram, and Olivier Guillon. “Ultra-Fast High-Temperature Sintering of Strontium Titanate.” Acta Materialia 231 (2022): 117918. https://doi.org/10.1016/j.actamat.2022.117918.


[i] Wang, Chengwei, Weiwei Ping, Qiang Bai, Huachen Cui, Ryan Hensleigh, Ruiliu Wang, Alexandra H. Brozena, et al. “A General Method to Synthesize and Sinter Bulk Ceramics in Seconds.” Science 368, no. 6490 (2020): 521–26. https://doi.org/10.1126/science.aaz7681.
[ii] Mishra, Tarini Prasad, Shufan Wang, Christian Lenser, Dylan Jennings, Moritz Kindelmann, Wolfgang Rheinheimer, Christoph Broeckmann, Martin Bram, and Olivier Guillon. “Ultra-Fast High-Temperature Sintering of Strontium Titanate.” Acta Materialia 231 (2022): 117918. https://doi.org/10.1016/j.actamat.2022.117918.