Application of Small-Crystal Diffraction Technique Using Synchrotron Radiation to Structural Studies of Ceramics

同步辐射小晶体衍射技术在陶瓷结构研究中的应用

基本信息

批准号：
07555191
负责人：
ISHIZAWA Nobuo
金额：
$ 2.5万
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 (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Both experimental and theoretical approaches to the cahrge density distribution study become more important in the field of materials science. However, several kinds of effects limit the accuracy of the observed kinematical structure factors from imperfect crystals. They are extinction, multiple scattering, absorption, counting statistics, thermal diffuse scattering, etc. The extinction and absorption can be reduced significantrly by using a smaller crystal and/or a shorter wavelength. Since both solutions tend to decrease the diffracted intensities, the use of synchrotron radiations is strongly recommended for accurate structure analyzes.In this study, we employed an improved single crystal diffraction technique to overcome the problems mentioned above. The technique has features of (1) using a small crystal of about 10mm in size, (2) using a vertically polarized synchrotron radiations at the beam line 14A equipped with a horizontal-type four-circle diffractometer suitable for the charge density study.Promising results have come out. For example, the three-dimensional diffraction data from a K_2NiF_4-type CaYAlO_4 single crystal of about 10mm in size have been found to be scarcely affected by the secondary extinction with a minimum value for the secondary extinction transmission factor Ys of 0.988 for the 200 strongest reflection. The value should be compared to 0.5855 calculated for a spherical specimen with diameter of 112mm mounted on the Ag rotating-anode four-circle diffractometer. The analysis of the extinction-free data on CaYAlO_4 provided detailed information about the composition, atomic positions and the electron density distribution, which have never been obtained by the conventional methods.Various structural studies were performed successfully on ceramic materials, such as BaTiO_3, lead-containing relaxr materials, CuInSe_2, MnS_2, LaTa_3O_9, LaNb_3O9 rare-earth sesquioxides, etc.

Cahrge密度分布研究的实验和理论方法在材料科学领域变得越来越重要。但是，几种效果限制了不完美晶体观察到的运动学结构因子的准确性。它们是灭绝，多个散射，吸收，计数统计，热弥散散射等。通过使用较小的晶体和/或较短的波长，可以显着降低灭绝和吸收。由于两种溶液都倾向于降低衍射强度，因此强烈建议使用同步加速器辐射进行准确的结构分析。在这项研究中，我们采用了改进的单晶衍射技术来克服上述问题。该技术具有（1）的特征，使用约10mm的小晶体，（2）使用配备有水平型四环衍射仪的垂直极化同步加速器辐射，适用于电荷密度研究。促进结果已经出现。例如，发现来自k_2nif_4型cayalo_4的三维衍射数据，大小约10mm的单晶几乎不会受到次级灭绝的影响，其次级灭绝透射因子ys的最小值为0.988的最小值为200最强的反射。该值应与对AG旋转轴上四环衍射仪上直径为112mm的球形试样计算的0.5855。 The analysis of the extinction-free data on CaYAlO_4 provided detailed information about the composition, atomic positions and the electron density distribution, which have never been obtained by the conventional methods.Various structural studies were performed successfully on ceramic materials, such as BaTiO_3, lead-containing relaxr materials, CuInSe_2, MnS_2, LaTa_3O_9, LaNb_3O9 rare-earth sesquioxides，等等。