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Study on γ-AlON Transparent Ceramic Doped by Mg2+/Li+

Author: LiuXiao
Tutor: WangZuo
School: Wuhan University of Technology
Course: Materials Physics and Chemistry
Keywords: MgAlON LiAlON Solid state reaction Pressureless Sintering Microstructure
CLC: TQ174.1
Type: Master's thesis
Year: 2011
Downloads: 44
Quote: 0
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Abstract


In recent years, it is found that Mg2+ and Li+ can be dissolved in the y-AlON. As a result, solid solution of MgAlON and LiAlON are formed. MgAlON and LiAlON transparent ceramics has the same crystal structure and excellent optical properties with that of y-AlON transparent ceramics. Some researches has proved that MgAlON and LiAlON transparent ceramics process some good properties such as better low-temperature thermal stability, mechanical properties and so on. So MgAlON and LiAlON transparent ceramics will have a more extensive application.In this thesis, Firstly, the mixture ratio of the raw powders are designed according to the relationship between vacancy concentration and the content of Mg2+/Li+ and N3- ion, as well as the phase diagram of MgO-AlN-Al2O3. The uniform LiAl5O8 nano-powders is prepared by sol-gel combined with low temperature self-combustion method. The MgAlON and LiAlON powders are synthesized by field assisted synthesis process, and the synthesis conditions, Mg2+/Li+ source and others have been optimized. The MgAlON and LiAlON powders with three compositions are synthesized under the most optimum condition, which lead to high purity, small and particle size uniform distribution.The MgAlON and LiAlON powders with three compositions are pressureless sintered to prepare MgAlON and LiAlON transparent ceramics. We study the influence of composition and sintering temperature on the microstructure and properties of MgAlON and LiAlON. The results showed that the best composition is 7#; the best sintering temperature for MgAlON is 1900℃; the suitable sintering temperature for LiAlON is 1925℃. The 7# MgAlON transparent ceramics sintered at 1900℃have good microstructure of homogeneous grain distribution and low porosity, which has relative density of 99.99%, maximum real in-line transmittances of 62%(thickness is 2 mm) in the region of 0.25-6μm, hardness of 14.3±0.3 GPa, modulus of elasticity of 320.32 MPa, dielectric constant of 9.85 MHz (at 1MHz).

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