Effect of Impurities and LiF Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel
Effect of Impurities and LiF Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel
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DOI：
10.1111/j.1744-7402.2012.02828.x
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发表时间：
2013-09-01
影响因子：
2.1
通讯作者：
Mueller, Mathis M.
中科院分区：
文献类型：
--
作者：
du Merac, Marc Rubat;Reimanis, Ivar E.;Mueller, Mathis M.
研究了杂质和LiF烧结助剂对热压透明镁铝尖晶石显微结构和光学性能的影响。较低和较高纯度的粉末进行热压，有和没有LiF和工艺参数的变化。微观结构进行了研究，使用光学和电子显微镜，光学性能，分光光度法，化学使用各种光谱技术。发现百万分之一的杂质在晶界处偏析并形成非晶相，限制晶粒生长并导致散射和不透明。发现LiF与杂质反应形成挥发性物质，其可以通过适当的处理去除，从而导致更大的晶粒尺寸和增加的透射率。LiF还抵消了由尖晶石还原引起的吸收，但导致MgO损失、晶界脆化，并且如果以较高浓度捕获，则限制晶粒生长并导致散射和不透明。
The effect of impurities and LiF sintering additive on the microstructure and optical properties of hot-pressed transparent MgAl2O4 spinel was investigated. A lower and a higher purity powder were hot pressed with and without LiF and process parameters varied. Microstructure was examined using optical and electron microscopy, optical properties using spectrophotometry, and chemistry using various spectroscopic techniques. Impurities present in parts-per million were found to segregate at grain boundaries and form an amorphous phase, restricting grain growth and causing scatter and opacity. It was found that LiF reacts with impurities to form volatile species that can be removed with proper processing, resulting in larger grain size and increased transmittance. LiF also counteracts absorption caused by reduction of spinel, but results in MgO loss, grain boundary embrittlement, and if trapped in higher concentration, restricts grain growth and causes scatter and opacity.