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Enhancement of analytical techniques of local structures in functional ceramic materials using synchrotron X-rays

使用同步加速器 X 射线增强功能陶瓷材料局部结构的分析技术

基本信息

批准号：
14550663
负责人：
ISHIZAWA Nobuo
金额：
$ 2.56万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

Both experimental and theoretical approaches to charge density studies have become increasingly important in the field of materials science. This is especially true for scientists seeking the origin of exotic physical properties of various ceramic materials. In the experimental approach, however, effects such as extinction, multiple scattering, absorption, counting statistics, and thermal diffuse scattering, have so far limited the accuracy of the experimental data. Recently we succeeded in the acquisition of virtually extinction-free diffraction data using small crystals at Photon Factory, High Energy Accelerator Research Organization in Tsukuba. Case studies are reported here for many technologically important compounds. One of our concerns was the K_2NiF_4-type structural family. Although about the role played by the Sr dopant in the phase transition mechanism. The present research redeems the lack of structural chemistry information about the effect of Sr doping on the phase transition from the charge density measurement by X-ray diffraction and various simulation techniques. The electron density distribution of La_<2-x>Sr_xCuO_4 with x approximately equal 1/8 determined at 297K using single-crystal synchrotron X-ray diffraction revealed not only the d_<x^2-y^2> orbital hole of Cu but also the disordered nature with tetragonal I4/mmm symmetry. These local structural disorders were confirmed by the molecular dynamics simulations.

电荷密度的实验和理论研究在材料科学领域变得越来越重要。这对于寻求各种陶瓷材料奇异物理特性起源的科学家来说尤其如此。然而，在实验方法中，诸如消光、多重散射、吸收、计数统计和热漫散射等效应迄今为止限制了实验数据的准确性。最近，我们在筑波的高能加速器研究机构光子工厂成功地获得了几乎无衍射的小晶体衍射数据。这里报告了许多技术上重要的化合物的案例研究。我们所关心的是K_2NiF_4型结构族。虽然关于Sr掺杂在相变机制中所起的作用。目前的研究弥补了缺乏结构化学信息的影响Sr掺杂的相变从电荷密度测量的X射线衍射和各种模拟技术。用<2-x>单晶同步辐射X射线衍射法测定了La_ Sr_xCuO_4（x = 1/8）在297 K时的电子密度分布，不仅揭示了Cu的d_<x^2-y^2>轨道空穴，而且揭示了Cu的无序性质，具有四元I_4/mmm对称性。分子动力学模拟证实了这些局部结构紊乱。