X-ray Powder Diffractometer Powder Diffraction of MgB2 sample MgB2 30 40 50 20 (degrees)
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第二章衍射分析 之三、X射线衍射分析的应用 第一节物相分析 第二节点阵常数的精确计算 第三节宏观应力的测量（选学） 第四节晶体取向的测定（选学） 12
12 第二章 衍射分析 之三、X射线衍射分析的应用 第一节 物相分析 第二节 点阵常数的精确计算 第三节 宏观应力的测量（选学） 第四节 晶体取向的测定（选学）
X射线衍射（XRD) 的应用 单一物相的鉴定 物相定性分析 物相分析 混合物相的鉴定 (物相鉴定)物相定量分析 点阵常数（晶胞参数)测定 晶体结构分析 晶体对称性（空间群)的测定 等效点系的测定 晶体定向、非晶体结构分析、晶粒度测定、 宏观应力分析
13 单一物相的鉴定 物相定性分析 物相分析 混合物相的鉴定 （物相鉴定） 物相定量分析 点阵常数（晶胞参数）测定 晶体结构分析 晶体对称性（空间群）的测定 等效点系的测定 晶体定向、非晶体结构分析、晶粒度测定、 宏观应力分析 X射线衍射（XRD）的应用
The figure below compares the X-ray diffraction patterns from 3 different forms of SiO, Counts SiO2 Glass 4000 2000 0 4000 Quartz 3000- 2000 1000 0 Cristobalite 4000 2000 20 30 40 Position [2Theta](Copper(Cu)) These three phases of SiO,are chemically identical Quartz and cristobalite have two different crystal structures The Si and O atoms are arranged differently,but both have structures with long-range atomic order The difference in their crystal structure is reflected in their different diffraction patterns The amorphous glass does not have long-range atomic order and therefore produces only broad scattering peaks 14
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Parallel planes of atoms intersecting the unit cell define directions and distances in the crystal. The(200)planes The (220)planes of atoms in NaCl of atoms in NaCl The Miller indices (hkl)define the reciprocal of the axial intercepts The crystallographic direction,[hkl],is the vector normal to(hkl) dok is the vector extending from the origin to the plane(hkl)and is normal to (hkl) The vector dhkl is used in Bragg's law to determine where diffraction peaks will be observed dhk is the vector drawn from the origin of the unit cell to intersect the crystallographic plane (hkl)at a 90angle dhk the vector magnitude,is the distance between parallel planes of atoms in the family(hkl) 5 d is a geometric function of the size and shape of the unit cell
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