Back refetions S 20 Frontreflections G 、S S
140 120 1 80 60 % 20 0 0 10203040 5060708090 100 26 2
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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 20 geometry is the most commonly used.The incident beam hits the sample in angleand 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衍射几何 设计原理：R1=R2=R,试样转0角，探测器转29角(20/0偶合)， 或试样不动，光管转6，探测器转0（日/8偶合） Tube Detector R2 聚焦圆 Sample 20 测量圆 要求：聚焦圆随衍射角大小而变化，衍射角越大、聚焦圆半径越小，当2日=0，聚焦圆半径r=∞； 当20=180时，聚焦圆r=R/2,且r=R/2sin0
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Focusing circles for various geometies 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 6
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The Bragg-Brentano Geometry Mono- chromator Divergence slit Antiscatter- 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. 2d sin0 =A Monochromator Slit Polychromatic Divergence Beam slit Monochromatic Beam Longer wavelengths Shorter Wavelengths 8 92 01 Monochromator Sufficient to separate Ka and KB .Not sufficient to separate Ka and Ko 8
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Powder Pattern Cell Structure Sample Instrument LLLLLL Unit Cell 20 6 Atomic Structure 20 + Sample Instrument .20 Powder Pattern .20
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La(NiasSn1s),Cu Ko 多 20 Diffractometers 1.5 8 113.Ka 1.0 032,Ka1 131,Ka 113.Ka 131,K 0.5 032.Ka Powder Diffractometer 鼍 10 0.0 80 83 84 0 30 40 60 60 708090100110120 Bragg angle,20(deg.) CAUTIO网 V.K.Pecharsky and P.Y.Zavalij Fundamentals of Powder Diffraction and Structural Characterization of Materials:
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