Oriented Nucleation of both Ge-Fresnoite and Benitoite/BaGe4O9 during the Surface Crystallisation of Glass Studied by Electron Backscatter Diffraction.
Oriented Nucleation of both Ge-Fresnoite and Benitoite/BaGe4O9 during the Surface Crystallisation of Glass Studied by Electron Backscatter Diffraction.
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DOI：
10.1038/srep20125
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发表时间：
2016-02-08
影响因子：
4.6
通讯作者：
Rüssel C
中科院分区：
文献类型：
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作者：
Wisniewski W;Patschger M;Murdzheva S;Thieme C;Rüssel C
将2 BaO - TiO2 - 2.75 GeO2和2 BaO - TiO2 - 3.67 GeO2玻璃（也称为BTG55）在680 ~ 970℃的温度下退火，诱导表面结晶。通过x射线衍射（XRD）和扫描电子显微镜（SEM），包括电子背散射衍射（EBSD）对所得样品进行了分析。在所有样品的直接表面都观察到Ge-Fresnoite (Ba2TiGe2O8， BTG)，并且在两种成分中都证明了取向成核。经过非常快速的动力学选择，BTG的晶体生长通过高度定向的枝晶进入体，其中c轴垂直于表面。取向层的生长最终被大块成核产生的枝晶BTG阻断。通过XRD和EBSD还在表面附近鉴定了二次相BaTiGe3O9 （benitoite）和BaGe4O9，这也表明了这些相的取向偏好。这种行为与先前的Ba2TiSi2O8以及Sr2TiSi2O8系统的报告形成对比。
Two glasses of the compositions 2 BaO - TiO2 - 2.75 GeO2 and 2 BaO – TiO2 –3.67 GeO2 (also known as BTG55) are annealed at temperatures from 680 to 970 °C to induce surface crystallization. The resulting samples are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD). Ge-Fresnoite (Ba2TiGe2O8, BTG) is observed at the immediate surface of all samples and oriented nucleation is proven in both compositions. After a very fast kinetic selection, the crystal growth of BTG into the bulk occurs via highly oriented dendrites where the c-axes are oriented perpendicular to the surface. The growth of this oriented layer is finally blocked by dendritc BTG originating from bulk nucleation. The secondary phases BaTiGe3O9 (benitoite) and BaGe4O9 are also identified near the surface by XRD and localized by EBSD which additionally indicates orientation preferences for these phases. This behaviour is in contrast with previous reports from the Ba2TiSi2O8 as well as the Sr2TiSi2O8 systems.