The effect of different sintering additives on the electrical and oxidation properties of Si3N4–MoSi2 composites |
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| Affiliation: | 1. Empa, Material Science and Technology, Laboratory for High Performance Ceramics, Ueberlandstrasse 129, Duebendorf CH-8600, Switzerland;2. Queen Mary, University of London, Mile End Road, London E2 4NS, UK;1. School of Metallurgical and Ecological Engineering University of Science and Technology Beijing, Beijing 100083, China;2. State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences, Beijing 100190, China;3. Department of Metallurgy, Graduate School of Engineering Tohoku University, Sendai 980-8579, Japan;1. Department of Mechanical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran;2. Young Researchers and Elite Club, Miyaneh Branch, Islamic Azad University, Miyaneh, Iran;1. Fraunhofer IKTS, Fraunhofer Institute for Ceramic Technologies and Systems, Winterbergstraße 28, 01277 Dresden, Germany;2. Carl Zeiss Microscopy GmbH, Carl-Zeiss-Straße 56, 73446 Oberkochen, Germany;1. Department of Materials Science and Engineering, Golpayegan University of Technology, Golpayegan, Iran;2. Department of Materials Science and Engineering, Tarbiat Modares University, PO Box 14115-143, Tehran, Iran;3. Faculty of Materials Engineering, Sahand University of Technology, Tabriz, Iran |
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| Abstract: | The fabrication and properties of electrically conductive Si3N4–MoSi2 composites using two different sintering additive systems were investigated (i) Y2O3–Al2O3 and (ii) Lu2O3. It was found that the sintering atmosphere used (N2 or Ar) had a critical influence on the final phase composition because MoSi2 reacted with N2 atmosphere during sintering resulting in the formation of Mo5Si3. The electrical conductivity of the composites exhibited typical percolation type behaviour and the percolation concentrations depended on the type of sintering additive and atmosphere used. Metallic-like conduction was the dominant conduction mechanism in the composites with MoSi2 content over the percolation concentrations due to the formation of a three-dimensional percolation network of the conductive MoSi2 phase. The effect of the sintering additives on the electrical and oxidation properties of the composites at elevated temperatures was investigated. Parabolic oxidation kinetics was observed in the composites with both types of additives. However, the Lu2O3-doped composites had superior oxidation resistance compared to the composites containing Y2O3–Al2O3. It is attributed to the higher eutectic temperature and crystallisation of the grain boundary phase and the oxidation layer in the Lu2O3-doped composites. |
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