X-Ray Measurement Methods

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X-Ray Measurement Methods From Chapter 6 of
Textbook 2 and other references
http//www.stanford.edu/group/glam/xlab/MatSci162_
172/LectureNotes/06_Geometry,20Detectors.pdf
Diffractometer Hull/Debye-Scherrer method Pinhole
method Laue Method Rotating Crystal Method
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Schematics of a typical X-ray diffractometer
S source C specimen H goniometer O
rotation axis A, B slits for collimation F
slit G detector E and H can be mechanically
coupled ? 2? and ? relation
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focusing monochromator
CM 2R, OC R Cut off the crystal behind the
dotted line to a radius R
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http//cheiron2008.spring8.or.jp/lec_text/Sep.30/2
008_T.Matsushita_1.pdf
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http//cheiron2008.spring8.or.jp/lec_text/Sep.30/2
008_T.Matsushita_1.pdf
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X-ray Optics
According to Euclid the angles in the same
segment of a circle are equal to one another and
the angle at the center of a circle is double
that of the angle at the circumference on the
same base, that is, on the same arc.
Bragg-Brentano diffractometers
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Modern Bragg-Brentano laboratory diffractometer
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Parallel beam geometry in Debye-Scherrer mode
using a double monochromator (DM) and an analyzer
crystal
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Single crystal
Polycrystal
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An ideal powder sample many crystallites in
random orientations smooth and constant
distribution of orientations Crystallites lt 10 µm
Sample preparation There are many methods
of preparing samples Sample should
normally be ground to lt 10 µm Sample may
be sieved to avoid large or small
crystallites Sample may be loaded into a
holder by pressing from the back while
using a slightly rough surface at the
front Sample may be pressed in from the
front Sample may be mixed with a binder
(epoxy or similar material) and then cut
and polished to give a suitable surface
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Hull/Debye-Scherrer method
Film
Film
2?S/R
S
2?
2?
S
R
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Film
Film
hole
S
S
2?
S
S
R
hole
2?
2?
2?
2?
2S
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Film
hole
S
2?
R
2?
2?
2?
and
Resolving power
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http//www.stanford.edu/group/glam/xlab/MatSci162_
172/LectureNotes/06_Geometry,20Detectors.pdf
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Pinhole photographs
D
D
F
F
2q
Incident X-Ray
A
C
A
r1
C
r2
S
B
B
180o-2q
tan2q r1/D
tan(180o-2q) r2/D
monochromatic or white radiation and powder
sample Laue methode white radiation and single
crystal
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Rotating Crystal Method
http//202.141.40.218/wiki/index.php/Unit-2_Intro
duction_to_X-ray_diffraction
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Concept of Ewald Sphere and Diffraction
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Wavelength incident beam diffracted
beam Magnitude of k ? the same 1/?.
Diffraction condition ?k G
?k? G?
?k G
2??B
2?B
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Diffraction Methods
Method ?
? Laue Variable
fixed Rotating crystal Fixed
Variable Powder Fixed
Variable
? vaied ? reciprocal lattice isrotated or
Ewald sphere is rotated
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Reciprocal lattice of polycrystalline sample
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Features of Rigaku TTRAX?
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