1.
XRD
Majed AMini
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2.
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When incident X-rays reach crystal atoms, they
get scattered, primarily through interaction with
the atoms’ electrons.
Under most angles of incidence, θ, the waves
reflected from neighbouring planes will show a
phase difference, leading to a cancellation of
amplitudes (destructive interferences).
X-ray diffraction according to W. L. Bragg

3.
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However, the waves reflected from neighbouring planes
add constructively in a few specific directions (they have
similar phase), as determined by Bragg’s law:
2dsinθ = nλ
Where d is the spacing between diffracting planes, θ is
the incident angle, n is an integer, and λ is the beam
wavelength.
The specific directions appear as spots on the
diffraction pattern called reflections. Consequently, X-
ray diffraction patterns result from electromagnetic waves
impinging on a regular array of scatterers.
X-ray diffraction according to W. L. Bragg

4.
X-ray diffractometers consist of three basic
elements: an X-ray source, a sample holder, and an
X ray detector.
In the source, an applied current heats up a
tungsten filament which releases electrons.
The released electrons are accelerated by high
voltage and hit a copper target where copper X-rays
are generated (Cu Kα X-ray source, CuKα
radiation = 1.5418Å).
The X-rays exit the tube and hit the sample holder.
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X-ray Diffraction (XRD) Instrumentation - How Does It Work?

5.
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These X-rays are directed onto the sample. As the
sample and detector are rotated, the intensity of the
reflected X-rays is recorded. When the geometry of
the incident X-rays impinging the sample
satisfies the Bragg Equation, constructive
interference occurs and a peak in intensity
occurs. A detector records and processes this X-ray
signal
The geometry of an X-ray diffractometer is such that
the sample rotates in the path of the collimated X-
ray beam at an angle θ while the X-ray detector is
mounted on an arm to collect the diffracted X-rays
and rotates at an angle of 2θ.
.
X-ray Diffraction (XRD) Instrumentation - How Does It Work?

6.
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2dsinθ = nλ
2θ ≈ 10°
λ=1.5418Å
N=1
2*d sin5=0.15418 nm
d= 0.884 nm
d for graphite: 0.335
XRD for GO