《材料测试技术及方法》课程教学课件（PPT讲稿）衍射分析——X射线衍射分析的应用

Back refetios S 20 Front refections 、S S

140 120 100 80 60 % 20 0 0 10203040 5060708090 100 26

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The Bragg-Brentano diffractometer 0-20 powder diffractometer Detector 20 X-ray source Analyser crystal Filters 2 Sample holder Divergence slit Receiving slit The Bragg-Brentano 0:20 geometry is the most commonly used.The incident beam hits the sample in angle 0 and reflected at the same angle. Hence the detector is placed at 20 from the incident beam.The detector rotates at twice angular speed than the sample

The Bragg-Brentano diffractometer The Bragg-Brentano :2 geometry is the most commonly used. The incident beam hits the sample in angle  and reflected at the same angle. Hence the detector is placed at 2 from the incident beam. The detector rotates at twice angular speed than the sample

Bragg-Brentano衍射儿何 设计原理：R1=R2=R,试样转8角，探测器转20角(20/0偶合)， 或试样不动，光管转0，探测器转0（0/8偶合) Tube Detector R2 聚焦圆 Sample 20 测量圆 要求：聚焦圆随行射角大小而变化，衍射角越大、聚焦圆半径越小，当2日=0，聚焦圆半径=∞； 当20=180时，聚焦圆r=R/2,且r=R/2sin0

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Focusing circles for various geometries G3 G2 Source Detector G1 Random powder mount (planes d1.d2.d3.) Goniometer ciicle

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View of an instrument Crystal Monochromator Detector X-Ray Tube

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The Bragg-Brentano Geometry Mono- Divergence slit Antiscatter- chromator slit Detector- Tube slit Sample

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Crystal Monochromator X-ray beam monochromatization can be achieved by diffraction from single crystals:Si,Ge,Licl,and graphite. 2dsin0=入 Monochromator Slit Polychromatic Divergence Beam slit Monochromatic Beam Longer wavelengths Shorter Wavelengths 8 61 02 01 Monochromator Sufficient to separate Ka and KB .Not sufficient to separate Ka and Ko

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Powder Pattern Cell +Structure Sample Instrument Unit Cell 20 + Atomic Structure 20 × Sample Instrument *20 Powder Pattern 9

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La(NiasSn1s),Cu Ko 多 20 Diffractometers 15 nsity,Y(1o 113,Ka 1.0 032.Ka1 131,Ka1 113.Ka 032.Ka 131,K 0.5 Powder Diffractometer 0.0 81 83 84 6 0 20 50 60708090100110120 Bragg angle,20(deg.) B V.K.Pecharsky and P.Y.Zavalyj Fundamentals of Powder Diffraction and Structural Characterization of Materials

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