The effect of texture(织构)
The effect of texture (织构 )
110 Random orientation 200 220 空 Preferred orientation 5 75 80 85g0g5 Abnormal increase of intensity of certain diffraction due to preferred orientation
35 40 45 50 55 60 65 70 75 80 85 90 95 Random orientation Preferred orientation (111) (200) (220) (311) Abnormal increase of intensity of certain diffraction due to preferred orientation
A single crystal specimen in a Bragg-Brentano diffractometer would produce only one family of peaks in the diffraction pattern. 10 20 25 30 35 40 45 [1101 Two-Theta (deg) [200小 20 At 20.620,Bragg's law The(110)planes would diffract at 29.3 The(200)planes are parallel to the (100) fulfilled for the (100)planes, 20;however,they are not properly planes.Therefore,they also diffract for this producing a diffraction peak aligned to produce a diffraction peak crystal.Since d2oo is %doo.they appear at (the perpendicular to those planes does 4220. not bisect the incident and diffracted beams).Only background is observed
A polycrystalline sample should contain thousands of crystallites. Therefore,all possible diffraction peaks should be observed. 8 (E 20 25 30 35 40 l2001 45 [100A [110 Two-Theta (deg) For every set of planes,there will be a small percentage of crystallites that are properly oriented to diffract (the plane perpendicular bisects the incident and diffracted beams). Basic assumptions of powder diffraction are that for every set of planes there is an equal number of crystallites that will diffract and that there is a statistically relevant number of crystallites,not just one or two