XRD课件 X射线衍射及其应用简介.ppt

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1、XRD课件课件 X射线衍射射线衍射及其应用简介及其应用简介X X射线衍射及其应用简介布拉格方程晶体对X射线的衍射X射线衍射方法 X射线衍射分析的应用 523341X射线的介绍X射线的介绍 X射线的介绍X射线的介绍X射线处于紫外线与 射线之间，测量其波长在约0.01到10nm范围内，用于衍射分析的X射线波长范围在0.05到0.25nm之间。X射线的介绍X X射线管是具有阴极和阳极的真空管，阴极用钨丝制成，通电后射线管是具有阴极和阳极的真空管，阴极用钨丝制成，通电后可发射热电子，阳极（就称靶极）用高熔点金属制成（一般用可发射热电子，阳极（就称靶极）用高熔点金属制成（一般用钨，用于晶体结构分析的钨，

2、用于晶体结构分析的X X射线管还可用铁、铜、镍等材料）。射线管还可用铁、铜、镍等材料）。用几万伏至几十万伏的高压加速电子，电子束轰击靶极，用几万伏至几十万伏的高压加速电子，电子束轰击靶极，X X射线射线从靶极发出。从靶极发出。 X射线的介绍常用的X射线光源l当一束X射线平面电磁波照射晶体时，晶体中原子周围的电子受X射线周期变化的电场作用而振动，从而使每个电子都变为发射球面电磁波的次生波源。所发射球面波的频率、位相（周相）均与入射的X射线相一致。基于晶体结构的周期性，晶体中各个电子的散射波可相互干涉相互叠加，称之为相干散射或衍射。布拉格方程1912年德国物理学家劳埃指出：当X射线照射晶体时，若要

3、在某方向上能获得衍射加强，必须同时满足三个劳埃方程及在晶体中三个相互垂直的方向上相邻源自散射线的波程差为波长的整数倍。劳埃方程式从本质上解决了X射线在晶体中的衍射方向问题，但其理论复杂，在使用上亦欠方便。布拉格方程晶体既然可看成有平行的原子面所组成，晶体的衍射线亦当是由原子面的衍射线叠加而得。这些衍射线会由于相互干涉而大部分被抵消，之其中一些可得到加强。更详细的研究指出，能够保留下来的那些衍射线，相当于某些网平面的反射线。按照这一观点，晶体对X射线的衍射可视为晶体中某些原子面对X射线的“反射”。布拉格方程波长为的X射线入射任一点阵平面上，在这一点阵平面上各个点阵点的散射波相互加强的条件是入射角

4、与反射角相等，入射线、反射线和晶面法线在同一平面上。布拉格方程将衍射看成是反射，是布拉格方程的基础。但衍射是基础，X射线只有在满足布拉个方程的角上才能放生反射，因此，这种反射亦称选择反射。 波长为的入射线，以角投射到晶体中间距为d的晶面时，有可能在晶面的反射方向上产生反射（衍射）线，其条件为相邻晶面的反射线的波程差为波长的整数倍。布拉格方程联系了晶面距d、掠射角角、反射级数n、X射线波长四个量。lBragg方程只确定衍射方向，衍射强度是由晶体一个晶胞中原子的种类、数目和排列方式决定的，整个晶体在各方向的衍射强度，实际上是一个晶胞衍射强度的若干倍。当然，仪器等实验条件对其数值也有影响。X射线衍射

5、方法 简化的布拉格方程维系着简化的布拉格方程维系着d d、及及三个参量。三个参量。相对于间距为相对于间距为d d的某种晶体而言，改变不同的的某种晶体而言，改变不同的或或值就会满足布拉格关系从而获得衍射。值就会满足布拉格关系从而获得衍射。一、劳埃法一、劳埃法二、周转晶体法二、周转晶体法三、粉末法三、粉末法X射线衍射方法 一、劳埃法一、劳埃法 劳埃法以光源发出连续X射线照射置于样品台上静止的单晶体样品，用平板底片记录产生的衍射线。根据底片位置的不同，劳埃法可以分为透射劳埃法和背射劳埃法。背射劳埃法不受样品厚度和吸收的限制，是常用的方法。劳埃法的衍射花样由若干劳埃斑组成，每一个劳埃斑相应于晶面的1n

6、级反射，各劳埃斑的分布构成一条晶带曲线。X射线衍射方法 二、二、周转晶体法周转晶体法周转晶体法以单色X射线照射转动的单晶样品，用以样品转动轴为轴线的圆柱形底片记录产生的衍射线，在底片上形成分立的衍射斑。这样的衍射花样容易准确测定晶体的衍射方向和衍射强度，适用于未知晶体的结构分析。周转晶体法很容易分析对称性较低的晶体（如正交、单斜、三斜等晶系晶体）结构，但应用较少。 X射线衍射方法 三、粉末法三、粉末法 粉末法是衍射分析中最常用的方法。大多数材料的粉末或其板、丝、块、棒等均可直接用作式样，其衍射花样有可提供很多的分析资料。粉末法主要用于测定晶体结构，进行物相定性、定量分析，精确测定晶体的点阵参数

7、以及材料的应力、织构、晶粒大小的测定等。 粉末法是各种多晶体X射线分析法的总称，其中以德拜-谢乐法最具典型性，它用窄圆筒底片来记录衍射花样，较重要的还有聚焦照相法等。X射线衍射分析的应用射线衍射分析的应用物相分析物相分析点阵常数的精确测定点阵常数的精确测定 晶粒尺寸和点阵畸变的测定晶粒尺寸和点阵畸变的测定应力的测定应力的测定 X X射线衍射分析应用射线衍射分析应用单晶取向和多晶织构测定等X射线衍射分析的应用1.1.物相分析物相分析晶体的射线衍射图像实质上是晶体微观结构的一种精细复杂的变换，每种晶体的结构与其射线衍射图之间都有着一一对应的关系，其特征X射线衍射图谱不会因为它种物质混聚在一起而产生

8、变化，这就是射线衍射物相分析方法的依据。制备各种标准单相物质的衍射花样并使之规范化，将待分析物质的衍射花样与之对照，从而确定物质的组成相，就成为物相定性分析的基本方法。鉴定出各个相后，根据各相花样的强度正比于改组分存在的量（需要做吸收校正者除外），就可对各种组分进行定量分析。目前常用衍射仪法得到衍射图谱，用“粉末衍射标准联合会（JCPDS）”负责编辑出版的“粉末衍射卡片（PDF卡片）”进行物相分析 。X射线衍射分析的应用PDF数据库检索与匹配X射线衍射分析的应用2.2.点阵常数的精确测定点阵常数的精确测定点阵常数是晶体物质的基本结构参数，测定点阵常数在研究固态相变、确定固溶体类型、测定固溶体溶

9、解度曲线、测定热膨胀系数等方面都得到了应用。点阵常数的测定是通过X射线衍射线的位置（）的测定而获得的，通过测定衍射花样中每一条衍射线的位置均可得出一个点阵常数值。X射线衍射分析的应用3.应力的测定应力的测定 射线测定应力以衍射花样特征的变化作为应变的量度。宏观应力均匀分布在物体中较大范围内，产生的均匀应变表现为该范围内方向相同的各晶粒中同名晶面间距变化相同，导致衍射线向某方向位移，这就是X射线测量宏观应力的基础；微观应力在各晶粒间甚至一个晶粒内各部分间彼此不同，产生的不均匀应变表现为某些区域晶面间距增加、某些区域晶面间距减少，结果使衍射线向不同方向位移，使其衍射线漫散宽化，这是X射线测量微观应

10、力的基础。X射线衍射分析的应用4.4.晶粒尺寸和点阵畸变的测定晶粒尺寸和点阵畸变的测定若多晶材料的晶粒无畸变、足够大，理论上其粉末衍射花样的谱线应特别锋利，但在实际实验中，这种谱线无法看到。这是因为仪器因素和物理因素等的综合影响，使纯衍射谱线增宽了。纯谱线的形状和宽度由试样的平均晶粒尺寸、尺寸分布以及晶体点阵中的主要缺陷决定，故对线形作适当分析，原则上可以得到上述影响因素的性质和尺度等方面的信息。 X射线衍射分析的应用衍射峰宽：晶粒尺寸衍射峰宽：晶粒尺寸X射线衍射分析的应用 5.单晶取向和多晶织构测定单晶取向和多晶织构测定 单晶取向的测定就是找出晶体样品中晶体学取向与样品外坐标系的位向关系。虽

11、然可以用光学方法等物理方法确定单晶取向，但X衍射法不仅可以精确地单晶定向，同时还能得到晶体内部微观结构的信息。一般用劳埃法单晶定向，其根据是底片上劳埃斑点转换的极射赤面投影与样品外坐标轴的极射赤面投影之间的位置关系。多晶材料中晶粒取向沿一定方位偏聚的现象称为织构，常见的织构有丝织构和板织构两种类型。为反映织构的概貌和确定织构指数，有三种方法描述织构：极图、反极图和三维取向函数，这三种方法适用于不同的情况。 X射线衍射仪产地：产地：德国德国布鲁克（布鲁克（AXS)AXS)公司公司型号：型号：D8 discoverD8 X射线衍射仪主要结构主要结构 光源：高压发生器与X光管 精密测角仪 光学系统

12、探测器X射线衍射仪封闭管光源封闭管光源X射线衍射仪测角仪系统测角仪系统X射线衍射仪配置的附件配置的附件(高温配件和薄膜配件高温配件和薄膜配件)X射线衍射仪 How do I incorporate my logo to a slide that will apply to all the other slides? On the View menu, point to Master, and then click Slide Master or Notes Master. Change images to the one you like, then it will apply to all

13、the other slides. X射线衍射仪 How do I incorporate my logo to a slide that will apply to all the other slides? On the View menu, point to Master, and then click Slide Master or Notes Master. Change images to the one you like, then it will apply to all the other slides. X射线衍射方法 How do I incorporate my log

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15、o be used within this PowerPoint template only. You may not extract the image for any other use. X射线衍射方法 How do I incorporate my logo to a slide that will apply to all the other slides? On the View menu, point to Master, and then click Slide Master or Notes Master. Change images to the one you like,

16、 then it will apply to all the other slides. Image information in product Image : Note to customers : This image has been licensed to be used within this PowerPoint template only. You may not extract the image for any other use. Hot Tip How do I incorporate my logo to a Hot Tip How do I incorporate

17、my logo to a slide that will apply to all the other slides? On the View menu, point to Master, and then click Slide Master or Notes Master. Change images to the one you like, then it will apply to all the other slides. Image information in product Image : Note to customers : This image has been lice

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19、 like, then it will apply to all the other slides. Image information in product Image : Note to customers : This image has been licensed to be used within this PowerPoint template only. You may not extract the image for any other use. Hot Tip How do I incorporate my logo to a slide that will apply t

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