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Defects and Orientation Dependent Transport in Orthosilicates

原硅酸盐中的缺陷和方向相关输运

基本信息

批准号：
5451553
负责人：
Professor Dr. Klaus Dieter Becker
金额：
--
依托单位：
Institut für Physikalische und Theoretische Chemie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2005
资助国家：
德国
起止时间：
2004-12-31 至 2010-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/5451553?language=en
关键词：
Defects Orientation Dependent Transport Orthosilicates

项目摘要

An optical spectroscopy study is proposed into the defect structure and the diffusion of defects in non-cubic orthosilicates of the type A2SiO4 with A = Co, Ni, Mn, which crystallize in the olivine structure. The spectroscopic experiments performed at high temperatures and defined oxygen activities will provide information on electronic defects (holes) and on the chemical diffusion responsible for redox processes in the material. Due to the orthorhombic structure of olivines, the kinetics for oxidation and reduction exhibits a pronounced dependence on crystal orientation. By comparison of chemical diffusion data with tracer diffusion data obtained by the American counterpart, a novel possibility is opened to determine the concentration of cation vacancies from transport data, which can then be compared with the direct data from thermogravimetry to elucidate details of the complex behavior of cation diffusion. The electrical conductivity of the transition metal orthosilicates will be measured as a function of temperature and oxygen activity for the different orientations of the crystals. In the framework of the small-polaron model, electrical conductivity is intimately related to the defect-induced contribution to optical spectra. From a comparison of these data detailed information is available on the microscopic mechanism and geometry of small-polaron hopping.

提出了对 A2SiO4 型非立方正硅酸盐（A = Co、Ni、Mn）中的缺陷结构和缺陷扩散的光谱研究，这些正硅酸盐以橄榄石结构结晶。在高温和定义的氧活度下进行的光谱实验将提供有关电子缺陷（空穴）和负责材料中氧化还原过程的化学扩散的信息。由于橄榄石的斜方结构，氧化和还原动力学表现出对晶体取向的明显依赖性。通过将化学扩散数据与美国同行获得的示踪扩散数据进行比较，开辟了一种新的可能性，可以根据传输数据确定阳离子空位的浓度，然后可以将其与热重分析的直接数据进行比较，以阐明阳离子扩散复杂行为的细节。过渡金属原硅酸盐的电导率将作为晶体不同取向的温度和氧活度的函数来测量。在小极化子模型的框架中，电导率与缺陷引起的光谱贡献密切相关。通过对这些数据的比较，可以获得有关小极化子跳跃的微观机制和几何形状的详细信息。