Densification behaviour and microstructural development in undoped yttria prepared by flash-sintering |
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| Affiliation: | 1. Department of Materials Science and Technology, Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan;2. National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan;3. Materials Design Innovation Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan;4. Department of Materials Science and Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan;5. Next Generation Zirconia Social Cooperation Program, Institute of Engineering Innovation, The University of Tokyo, Bunkyo, Tokyo 113-8656, Japan;1. Department of Materials Science and Engineering, Rutgers University, Piscataway, NJ 08854, United States;2. Argonne National Laboratory, Advanced Photon Source, Lemont, IL 60439, United States |
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| Abstract: | Conventional sintering of undoped Y2O3 requires temperatures above 1400 °C for a few hours. We show that it can be sintered nearly instantaneously to nearly full density at furnace temperature of 1133 °C under a DC applied field of 500 V/cm. At 1000 V/cm sintering occurs at 985 °C. The FLASH event, when sintering occurs abruptly, is preceded by gradually accelerated field-assisted sintering (FAST). This hybrid behaviour differs from earlier work on yttria-stabilized zirconia where all shrinkage occurred in the flash mode. The microstructure of flash-sintered specimens indicated that densification was accompanied by rapid grain growth. The single-phase nature of flash-sintered Y2O3 was confirmed by high-resolution transmission electron microscopy. The non-linear rise in conductivity accompanying the flash led to Joule heating. It is postulated that densification and grain growth were enhanced by accelerated solid-state diffusion, resulting from both Joule heating and the generation of defects under the applied field. |
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| Keywords: | Yttria Flash-sintering Electron microscopy Diffusion |
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