首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Crystal structure and microstructure of synthetic hexagonal magnesium-cobalt cordierite solid solutions (Mg_(2-2x) Co_(2x) Al_4Si_5O_(18))
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Crystal structure and microstructure of synthetic hexagonal magnesium-cobalt cordierite solid solutions (Mg_(2-2x) Co_(2x) Al_4Si_5O_(18))

机译:合成六角型镁钴堇青石固溶体(Mg_(2-2x)Co_(2x)Al_4Si_5O_(18)的晶体结构和微观结构

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摘要

Co~(2+)-containing cordierite glasses, of nominal compositions (Mg_(1-x) Co_x)_2Al_4Si_5O _(18) (withx = 0, 0.2, 0.4, 0.6, 0.8 and 1), were prepared by melting colloidal gel precursors. After isothermal heating at 1273K for around 28h, a single-phase α-cordierite (high-temperature hexagonal polymorph) was synthesized. All materials were investigated using X-ray powder diffraction and field-emission scanning electron microscopy. The crystal structure and microstructure were determined from X-ray diffraction patterns. Rietveld refinement confirmed the formation of magnesium-cobalt cordierite solid solutions. The unit-cell volume increased with the increase of cobalt content in the starting glass. The crystalline microstructure of the cordierites was interpreted using a mathematical model of a polycrystalline material and characterized by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice-strain distribution. Hexagonal prismatic was the prevalent shape of α-cordierite crystallites. Bimodality in the size distribution was observed and interpreted as a consequence of two paths of the crystallization: the nucleation from glass of μ-cordierite, which transformed into α-cordierite with annealing, or the nucleation of α-cordierite directly from glass at high temperatures. Scanning electron microscopy images agreed well with crystalline microstructure characteristics determined from the X-ray diffraction line-profile analysis.
机译:通过熔化胶体凝胶制备标称组成为(Mg_(1-x)Co_x)_2Al_4Si_5O_(18)(withx = 0、0.2、0.4、0.6、0.8和1)的含Co〜(2+)堇青石玻璃前体。在1273K下等温加热约28小时后,合成了单相α-堇青石(高温六角形多晶型物)。使用X射线粉末衍射和场发射扫描电子显微镜对所有材料进行了研究。由X射线衍射图确定晶体结构和微观结构。 Rietveld精制方法证实了镁钴堇青石固溶体的形成。随着原始玻璃中钴含量的增加,晶胞体积增加。使用多晶材料的数学模型解释堇青石的晶体微观结构,并以普遍的微晶形状,体积加权的微晶尺寸分布和二阶晶格应变分布为特征。六角棱柱形是α-堇青石微晶的普遍形状。观察到并解释了尺寸分布的双峰性,这是两个结晶路径的结果:μ-堇青石的玻璃成核,并通过退火转变为α-堇青石,或在高温下直接从玻璃中成核的α-堇青石。 。扫描电子显微镜图像与由X射线衍射线轮廓分析确定的晶体微观结构特征非常吻合。

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