Glass-to-crystal transition of sodium(Na) super ionic conductors (NASICON)

钠（Na）超离子导体的玻璃到晶体转变（NASICON）

• 批准号: 422320128
• 负责人: Dr. Henry Auer
• 金额: --
• 依托单位: Department of Physics
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/422320128?language=en
• 关键词: Glass; crystal; transition; sodium; Na

The glass-to-crystal transition of sodium (Na) super ionic conductors (NASICON) will be investigated by total scattering and Bragg-diffraction techniques. Two substitution series will be studied: Na_(1+x)Al_xGe_(2-x)P_3O_12 and Na_(1+x)Ti_2P_(3-x)Si_xO_12 (x = 0 to 2). These materials are relevant as solid-electrolytes or as electrode materials in sodium-based batteries which are discussed as a replacement for lithium-based ones. NASICON materials benefit strongly from a preparation by a glass-ceramic synthesis. Nevertheless, the glass structures are hardly investigated. Crystal structures were only studied for sintered materials. Thus, the glass-ceramics are structurally not well characterized as well. Amorphous residues are not determined but will lead to compositional changes in the crystalline phases. The proposed work aims to determine the atomic structure of NASICON-glasses by scattering techniques for the first time. Structural ordering on different length scales of the glass phases can be determined from reciprocal-space data, i.e., from the behavior of the first sharp diffraction peak. Bond lengths and coordination numbers will be extracted from the pair-distribution function (real-space) obtained by Fourier transformation of the scattering data. 3-D atomic models will be refined to experimental data by the reverse Monte-Carlo method. Additional constraints, e.g., on coordination numbers, will be provided by complementary experiments, e.g. solid-state NMR. This will lead to detailed knowledge of the atomic structure which is a prerequisite to interpret the strength of ionic bonding and, therefore, ionic mobility. The ceramic products will be characterized regarding exact compositions of the crystalline phases and amorphous residues by the Rietveld technique. A Re-determination of crystal structures, especially regarding substitutions and coordination environments, will provide a reference point for the structural work on the glass phases. These materials show a homogeneous nucleation. Such a mechanism in was not investigated for non-siliceous systems, yet. A total scattering approach on differently annealed samples at the threshold of crystallization will provide insights into structural reorganization of the glasses during the nucleation process. The understanding of changes of the local environments from glass to crystalline state will help to guide the development of new fast ion-conducting glasses and ceramics. Furthermore, experimental data will help to develop and validate predictive models that are still inadequate for non-crystalline materials. Finally, a high temperature total scattering experiment will be done to monitor crystallization in situ. Synchrotron based rapid acquisition PDF (RAPDF) is the method of choice to study changes in the glassy phase as well as the formation and composition of crystalline phases. This will give us a comprehensive understanding of the formation of the glass-ceramics.

用全散射和布拉格衍射技术研究了钠(Na)超离子导体(NASICON)的玻璃到晶体的转变。研究了两个取代系列：Na_(1+x)Al_xGe_(2-x)P_3O_12和Na_(1+x)Ti_2P_(3-x)Si_xO_12(x=0~2)。这些材料作为固体电解液或作为钠基电池的电极材料被讨论为锂基电池的替代品。NASICON材料从微晶玻璃合成的制备中受益匪浅。然而，对玻璃结构的研究却很少。只研究了烧结材料的晶体结构。因此，微晶玻璃在结构上也没有得到很好的表征。不确定无定形残留物，但会导致晶相的成分变化。这项拟议的工作旨在首次用散射技术确定NASICON玻璃的原子结构。玻璃相在不同长度尺度上的结构有序性可以根据倒易空间数据，即根据第一个尖锐衍射峰的行为来确定。通过对散射数据进行傅里叶变换，从对分布函数(实空间)中提取键长和配位数。用逆蒙特卡罗方法将三维原子模型修正为实验数据。补充实验将提供额外的限制，例如对配位数的限制，例如固体核磁共振。这将导致详细的原子结构知识，这是解释离子键强度和离子迁移率的先决条件。通过Rietveld技术，将对陶瓷产品的晶相和无定形残留物的准确组成进行表征。重新确定晶体结构，特别是关于取代和配位环境，将为玻璃相的结构工作提供一个参考点。这些材料表现出均匀的形核。这种机理在非硅体系中还没有被研究过。在晶化临界点对不同退火态的样品进行全散射的方法将有助于深入了解玻璃在成核过程中的结构重组。了解局部环境从玻璃到晶态的变化，将有助于指导新型快离子导电玻璃和陶瓷的发展。此外，实验数据将有助于开发和验证仍然不适用于非晶态材料的预测模型。最后，还将进行高温全散射实验，以实时监测结晶情况。基于同步加速器的快速采集PDF(RAPDF)是研究玻璃相的变化以及晶相的形成和组成的首选方法。这将使我们对微晶玻璃的形成有一个全面的了解。