Backrfetions S 20 Frontrefections
140 120 100 60 40 20 0 0 102030405060708090 100 26
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The Bragg-Brentano diffractometer 0-20 powder diffractometer Detector 20 X-ray source Analyser crystal Filters Sample holder Divergence slit Receiving slit The Bragg-Brentano:20 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 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20角(20/0偶合)， 或试样不动，光管转0，探测器转0(0/9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=∞； 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 00只 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
6 View of an instrument
The Bragg-Brentano Geometry Mono- chromator Divergence slit Antiscatter- slit Detector- Tube slit Sample 7
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Crystal Monochromator X-ray beam monochromatization can be achieved by diffraction from single crystals:Si,Ge,Licl,and graphite. 2dsin= Monochromator Slit Polychromatic Divergence Beam slit Monochromatic Beam Longer wavelengths Shorter Wavelengths 62 61 01 Monochromator Sufficient to separate Ka and KB Not sufficient to separate Ko and Ko
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Powder Pattern Cell Structure Sample Instrument Unit Cell 28 + 山 Atomic Structure 20 + Sample Instrument →20 A人MW Powder Pattern 26 9
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La(NiasSn 1s),Cu Ko 25 20 Diffractometers 1.5 15 10 113.Ka ￥032,Ka1 131,Ka 113.Ka 0.5 032.Ka2 /131,Ka Powder Diffractometer 0 0.0 80 81 83 83 84 0 20 30 40 50 708090100110120 Bragg angle,20(deg.) V.K.Pecharsky and P.Y.Zavalii Fundamentals of Powder Diffraction and Structural Characterization of Materials
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