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Microstructural evolution and relevant mechanical properties of Al-rich transparent magnesium aluminate ceramics
Affiliation:1. Engineering Ceramics Research Group, Korea Institute of Materials Science, 797 Changwondaero, Changwon, Gyeongnam, 51508, Republic of Korea;2. Department of Nano Materials Engineering, Kyungnam University, Changwon, Republic of Korea;3. Agency for Defence Development, Yuseong P.O. Box 35, Daejeon, 34186, Republic of Korea;1. Université Paris 13, Sorbonne Paris Cité, Laboratoire de Sciences des Procédés et des Materiaux, CNRS UPR-3407, 93430 Villetaneuse, France;2. Université Paris 13, Sorbonne Paris Cité, Laboratoire de Physique des Lasers, CNRS UMR-7538, 93430 Villetaneuse, France;3. Université de Tours, Laboratoire GREMAN, CNRS – INSA - CVL UMR-7347, IUT de BLOIS, 15 rue de la Chocolaterie CS 32903, 41029 Blois Cedex, France;4. Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411, Tartu, Estonia
Abstract:A novel phenomenon is found that the grain growth of aluminum-rich magnesium aluminate is suppressed to 5 μm, despite of high-temperature hot-isostatic-press at 1750 °C. For the transparent MgO-nAl2O3 (n = 1.2, 1.5, 2.0), the transmittance and strength tended to be enhanced with increasing Al2O3 content, having the highest values 80 % at 550 nm and 214.3 MPa for n = 2.0. This is due to the different microstructural evolution depending on the composition. When the excessive Al2O3 was small, the inhomogeneous microstructure with bimodal grain size and lots of rod-shaped particles were observed. However, as the Al2O3 amount increased, the microstructure became homogeneous with reducing the grain size and the rod-shaped particles. The microstructural and compositional analysis revealed that the rod-shaped particle were generated due to the trace potassium impurity as well as the different cationic diffusion rate, and the suppression of grain growth was induced by the severe Al segregation at the grain-boundaries.
Keywords:Magnesium aluminate  Transparent ceramics  Mechanical properties  Transmittance  Grain growth
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