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1、第四讲 衍射仪和物相定性分析,X-ray Diffraction,XRD is based on the interference effect from the scattered radiation by the different locations of atoms in matter.XRD method is one of the most powerful nondestructive tools for investigation of structural properties of various materials,提纲,X射线衍射方法衍射仪衍射仪的构造和衍射几何X射线衍
2、射仪测角仪简图（光路系统示意图）衍射仪的工作方式XRD物相定性分析原理PDF卡片PDF卡片索引方法步骤和注意事项,X射线衍射方法,X射线衍射方法,研究单晶体的衍射方法,粉末或多晶体衍射方法,Tube,Powder,Film,单色X射线粉末照相法（粉末法、粉晶法）：用照相底片记录衍射图；衍射仪法：用计数器来记录衍射图。,粉末或多晶体衍射方法,德拜法：Debye-Sherrer Camera,粉末或多晶体衍射方法,衍射仪法,衍射仪,日本理学公司RIGARGU德国BRUKER荷兰Philips瑞士ARL,衍射仪,D8 ADVANCE Bragg-Brentano Diffractometer（德国B
3、RUKER公司),X射线粉末衍射仪构造示意图,X射线多晶衍射仪由射线发生器、测角仪、射线强度测量系统以及衍射仪控制与衍射数据采集、处理系统四大部分组成。,衍射仪组成,衍射仪组成,衍射仪结构图,衍射仪内部示意图,Classical Powder diffractometer,Tube,Divergenceslit,Mask,Sample stage,Sample,Goniometer,Receiving slit,Monochro-mator,Detector,Classical Powder Diffractometer,Basic Optics,X-ray tube focus,Primar
4、y filter*,Primary Soller slits,Divergence slit,Width mask,Sample,Receiving slit,Secondary Soller slits,Anti scatter slit,Secondary filter*,Detector,Primary,Secondary,*only one filter is required,Calassical Powder Diffractometer,Basic optics,Basic Geometry of a diffractometer without monochromator,Pr
5、ogrammable Bragg-Brentano Optics,Optics,Classical Powder Diffractometer,Geometry with monochromator,测角仪简介,测角仪是X射线的核心组成部分试样台位于测角仪中心，试样台的中心轴ON与测角仪的中心轴(垂直图面)O垂直。试样台既可以绕测角仪中心轴转动，又可以绕自身中心轴转动。,测角仪,绕角仪工作动态图,单色光源?,单色器monochromator,How to remove K?,滤波片和单色器,滤波片工作原理,滤波片的选择:(1)它的吸收限位于辐射源的K和K 之间，且尽量靠近K。强烈吸收K，K吸收
6、很小；(2)滤波片的以将K强度降低一半最佳。Z靶40时 Z滤片=Z靶-2；阳极靶的选择:（1）阳极靶K波长稍大于试样的K吸收限；（2）试样对X射线的吸收最小。Z靶Z试样+1。,单色器（monochromator）,Completely remove of K,partly separate K1 and K2,样品制备（Sample preparation）,The total number of spherical particles in a cylindrical specimen 10mm In diameter and 0.1mm deep as a function of part
7、icle size assuming close Packing of the spheres.D-Diameter,h-specimen depth and d-particle diameter,Grinding and mechanical mill,Infinite number of possible orientation of the particlesPowder mounting to avoid orientation,Flat sample holders,衍射仪的工作方式连续扫描：探测器以一定角速度在选定的角度范围内连续扫描。优点：快速、方便。缺点：峰位偏移、分辨率降低
8、、线型畸变。,衍射仪的工作方式步进扫描,步长(步宽)表示每步扫描的角度,停留时间改变调节扫描速度的快慢。无滞后和平滑效应。峰位准确分辨力好。,Recording the XRD pattern with,Suitable radiationUnder Suitable voltage and current conditionMust ensure thatIdeal fine grain size-sharp and intense peak with minimum of backgroundNo preferred orientation in the specimen,X-射线物相定性
9、分析,理论基础卡片索引定性分析的步骤定性分析的注意事项,X射线物相定性分析,Basic concept of XRD,The relationship between the crystal structure and x-ray diffraction phenomenaCrystal structure,Unit cell,Atomic positions,x-ray diffraction pattern,Line positions,Line intensities,The unit cell size and shape determine positions of diffract
10、ion peaks,and vice versa,The atom positions determine the peak intensities,and vice versa,理论依据,晶体有特定的晶体结构（参数），包括结构类型、晶胞形状和大小；晶胞中原子、离子或分子的种类、数目和位置；晶体对一定波长的x射线的衍射产生带有晶体特征的特定衍射花样，即衍射位置和衍射强度（d-I数据组），也就是说晶体物质和其衍射花样一一对应，“指纹特征”；Fingerprint=unambiguous identification两种或两种以上的晶体的混合物，每种物质特有的衍射花样不变，相互独立，互不干扰。多相
11、试样的衍射花样只是所含物质衍射花样的简单叠加。,即：结晶物质具有自己特定的原子种类、原子排列方式和点阵参数，进而呈现特定的衍射花样；diffraction pattern is determined by the exact atomic arrangement in a materials,so it is like a“fingerprint”of the material.多相物质衍射花样互不干扰、相互独立，只是机械叠加；Each substance in a mixture produces its own characteristic diffraction pattern inde
12、pendently of the others.衍射花样可表明物质中元素的化学结合态。1919 A W Hull,A new method of chemical analysis,J.Am.Chem.Soc.41(1919),1168,1919 A W Hull,A new method of chemical analysis,J.Am.Chem.Soc.41(1919),1168,every crystalline substance gives a pattern;that the same substance always gives the same pattern;and tha
13、t in a mixture of substances each produces its pattern independently of the others,so that the photograph obtained with a mixture is the superimposed sum of the photograph that would be obtained by exposing each of the components separately for the same length of time.This law applies quantitatively
14、 to the intensities of the lines,as well as to their positions,so that the method is capable of development as quantitative analysis.,过 程,把晶体全部进行衍射或照相，再将其存档（标准数据库）；a large collection of XRD patterns from a number of materials 实验时只要把试样的衍射花样与标准的衍射花样对比，选择相同者即可；Compare and match定性分析实验就是信息（花样）的采集处理和查找和查找
15、核对标准花样两件事情。,标准数据库JCPDS卡片（PDF）,起源：衍射花样不便于保存和交流，尤其拍摄条件不同，其花样形态也大不一样，因此要有一国际上通用的花样标准，反映晶体衍射本质不因试验条件而变化的特征，而d-I数据组满足此要求，代替衍射花样。将衍射花样特征数字化，制成卡片。1938年，哈那瓦特最先发起以d-I数据组代替衍射花样制备衍射数据卡片；1941年，美国ASTM 接管该工作，出版了1300张卡片，称ASTM卡片或PDF卡片，至1963年出版了13集，以后每年一集；1969年，国际粉末衍射标准联合会（Joint Committee on Powder Diffraction Stand
16、ards)成立，和“国际衍射资料中心”（ICDD-International centre for Diffraction Data）联合出版；目前无机70000多张，有机20000多张。,粉末衍射卡组：PDF(the power diffraction file),粉末衍射标准联合委员会：JCPDS（the joint committee on power diffraction standards),The cards list the interplanar spacings(d values)and not 2 theta values,why?,PDF 索引（Indexes for
17、PDF）,哈那瓦特索引（Hanawalt Index）芬克索引（Fink Index）字顺索引（Alphabetical Index）矿物名称索引（Mineral Name Index）,Hanawalt Indexnumerical search manual,Lists the compounds in decreasing order of the d spacings of the eight most intense reflectionsThese d spacings are arranged in groups starting from 999.9A to 8.00 A(+/
18、-0.20A)as one group,7.99 to 7.00A as another group,down to 1.37 to 1.00A(+/-0.01A);The d value of the strongest peak determines the group into which the entry falls,second strongest,subgroup;Most useful in the identification of an unknown specimen,Single-phase material,Group 2.222.16(+/-0.01)A,All p
19、eaks must match well,Two-phase material,Complex and time consuming,Group 2.152.09(+/-0.1）A,None gives 2.03Athe third strongest peak,局限性（limitations）,In practice,the intensities of all the peaks may not always match those listed on the standard cards,due toMaterial may developed texture(preferred ori
20、entation),some peaks higher,others lowerThe sequence of d spacing with decreasing intensity may be wrong,if experimental pattern was not recorded in the full range of 2 thetaThe cards in the PDF may have some errorsThe method is totally inadequate for identification if the diffraction pattern of the
21、 substance is not in the PDF,数据记录处理,寻峰,PDF寻取、注册,数据比对,注意事项,D值数据比相对强度数据重要；低角区数据比高角区数据重要（2dsin=）；了解试样的来源、化学成分和物理特性有助于正确判断；与其它方法结合；多相或混合试样勿求所有衍射线全部核对；低含量相进行富集浓缩。,Index with computer,Very popular and being widely used today!,1.pcpdgwin2.search match 3.high score 4.jade Sometimes,data transformation is ne
22、cessary!,原始数据的初步处理,1.图谱的平滑2.背底的扣除3.衍射峰的辨认4.各晶面族的衍射角2的实验值测定5.衍射强度I的测量,XRD常用 软件比较,1.pcpdgwin最原始。它是在衍射图谱标定以后，按照d值检索。一般可以有限定元素、按照三强线、结合法等方法。所检索出的卡片多时候不对。一张复杂的衍射谱有时候一天也搞不定。2.search match可以实现和原始实验数据的直接对接，可以自动或手动标定衍射峰的位置，对于一般的图都能很好的应付。而且有几个小工具使用很方便。如放大功能、十字定位线、坐标指示按钮、网格线条等。最重要的是它有自动检索功能。可以帮你很方便的检索出你要找的物相。也
23、可以进行各种限定以缩小检索范围。如果你对于你的材料较为熟悉的话，对于一张含有4，5相的图谱，检索也就3分钟。效率很高。而且它还有自动生成实验报告的功能！,XRD常用 软件比较,3.high score几乎search match中所有的功能，highscore都具备，而且它比searchmatch更实用。（1）它可以调用的数据格式更多。（2）窗口设置更人性化，用户可以自己选择。（3）谱线位置的显示方式，可以让你更直接地看到检索的情况（4）手动加峰或减峰更加方便。（5）可以对衍射图进行平滑等操作，是图更漂亮。（6）可以更改原始数据的步长、起始角度等参数。（7）可以进行0点的校正。（8）可以对峰的外形进行校正。（9）可以进行半定量分析。（10)物相检索更加方便，检索方式更多。（11）可以编写批处理命令，对于同一系列的衍射图，一键搞定。,XRD常用 软件比较,4.jade和highscore相比自动检索功能少差，但它有比之更多的功能。（1）它可以进行衍射峰的指标化。（2）进行晶格参数的计算。（3）根据标样对晶格参数进行校正。（4）轻松计算峰的面积、质心。（5）出图更加方便，你可以在图上进行更加随意的编辑。,Search-match,Manual ppt attachedSoftware can be downloaded freely,
