Evolution of core–rim structures and phase transformations in infra-red transmitting Y-α-SiAlON ceramics |
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| Affiliation: | 1. School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China;2. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100080, China;1. School of Mechanical Engineering, Sichuan University, Chengdu, 610065, China;2. State Key Laboratory of Nuclear Fuel and Materials, China Nuclear Power Institute, 610065, China;3. College of Material Science and Engineering, Chengdu, 610065, China;4. School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China;5. Chengdu Keningda Materials Co., Chengdu, 610065, China;6. The Second Research Institute of Civil Aviation Administration of China, Chengdu, 610041, China;1. Functional Ceramics Laboratory, Department of Materials Science and Engineering, The University of Seoul, Seoul 02504, Republic of Korea;2. Nuclear Fuel Technology Department, KEPCO Nuclear Fuel, Daejeon 34057, Republic of Korea;1. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;2. Buildings and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;3. Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA;4. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;1. School of Materials Science and Engineering, Yeungnam University, Gyeongsan, 38541, South Korea;2. Institute for Rare Metals & Division of Advanced Materials Engineering, Kongju National University, Cheonan, 32588, South Korea |
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| Abstract: | Core–rim structures were observed as common features in Y-α-SiAlON ceramics hot-pressed between 1550?1950 °C. We found most dopants were taken into α’-rims, and a transition layer grown first on α-cores from liquid-phase over-saturated with metal solutes. Elongated β’-grain were formed as minor phase with α’- or AlN-cores thus only after the α’ matrix had consumed up all Y solutes, revealing that the α’ → β’ transformation is controlled by the transient liquid-phase and similar defects and dangling bonds could be detected in both SiAlON phases by cathodoluminescence. Quantitative assessment of Ym/3Si12?(m+n)Alm+nOnN16?n demonstrates the multiphase evolution, initiated by over-saturation of Y solutes at low temperatures thus retaining α-phase as cores to lower the infra-red transmittance, dictated by homogenization of Al solutes at higher temperature. The elimination of those phase boundaries leads to better dopant and sintering design for achieving transparent and high-performance SiAlON ceramics. |
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| Keywords: | α-SiAlON ceramics Core–rim structures Phase transformation Liquid phase sintering Infrared transmittance |
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