The document discusses X-ray fluorescence (XRF) theory and applications. XRF involves bombarding a sample with X-rays, which causes fluorescent X-rays to be emitted from the sample that are characteristic of its elemental composition. This allows for both qualitative and quantitative elemental analysis. Key advantages of XRF include rapid, nondestructive analysis of major and trace elements in various materials. Common applications include analysis of soils, minerals, metals, and more in fields like geology, archaeology, and environmental analysis.

1. University of Dicle
Faculty of Science
Department of Physics
XRF
Theory and Appliication
Prepared by
Sirwan S. Hasan
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2. XRF Introduction :-
• X-ray fluorescence (XRF) is the emission of characteristic
"secondary" (or fluorescent) X-rays from a material that has
been excited by bombarding with high-energy X-rays or
gamma rays,.
• It works on wavelength-dispersive spectroscopic principles
that are similar to an electron microprobe (EPMA). However,
an XRF cannot generally make analyses at the small spot sizes
typical of EPMA work (2-5 microns), so it is typically used for
bulk analyses of larger fractions of geological materials.
• The relative ease and low cost of sample preparation, and the
stability and ease of use of x-ray spectrometers make this one
of the most widely used methods for analysis of major and
trace elements in rocks, minerals, and sediment.
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3. • When an element is placed in a beam of x-rays, the x-rays are absorbed.
The absorbing atoms become ionized (e.g. due to the x-ray beam ejects
the electron in the inner shell).
• An electron from higher energy shell (e.g., the L shell) then fall into the
position vacated by dislodged inner electron and emit x-rays or
characteristic wavelength.
• This process is called x-ray fluorescence.
• The wavelength of fluorescence is characteristic of the element being
excited, measurement of this wavelength enable us to identify the
fluorescing element.
• The intensity of the fluorescence depends on how much of that element
is in x-ray beam.
• Hence measurement of the fluorescence intensity makes possible the
quantitative determination of an element.
• The process of detecting and analyzing the emitted x-rays is called “X-
ray Fluorescence Analysis.”
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XRF Theory

4. • In most cases the innermost K and L shells are involved in XRF
detection.
• A typical x-ray spectrum from an irradiated sample will display
multiple peaks of different intensities.
• The characteristic x-rays are labeled as K, L, M or N to denote
the shells they originated from.
• Another designation alpha (α), beta (β) or gamma (γ) is made to
mark the x-rays that originated from the transitions of electrons
from higher shells.
• Hence, a Kα x-ray is produced from a transition of an electron
from the L to the K shell, and a Kβ x-ray is produced from a
transition of an electron from the M to a K shell, etc.
• Since within the shells there are multiple orbits of higher and
lower binding energy electrons, a further designation is made as
α1, α2 or β1, β2, etc. to denote transitions of electrons from these
orbits into the same lower shell.
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5. 5
K & L Spectral Lines
 K - alpha lines: L shell e-
transition to fill a vacancy
in K shell. Most frequent
transition, hence most
intense peak.
 K - beta lines: M shell e-
transitions to fill a vacancy
in K shell.
 L - alpha lines: M shell e-
transition to fill a vacancy
in L shell.
 L - beta lines: N shell e-
transition to fill a vacancy
in L shell.
L Shell
K Shell
K alpha
K beta
M Shell
L alpha
N Shell
L beta

6. The XRF Process
Example: Titanium Atom (Ti = 22)
1) An electron in the K shell is
ejected from the atom by an
external primary excitation
x-ray, creating a vacancy.
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7. 2) An electron from the L or
M shell “jumps in” to fill the
vacancy.
In the process, it emits a
characteristic x-ray unique to
this element and in turn,
produces a vacancy in the L
or M shell.
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8. 3) When a vacancy is created
in the L shell by either the
primary excitation x-ray or
by the previous event, an
electron from the M or N
shell “jumps in” to occupy
the vacancy. In this process,
it emits a characteristic x-ray
unique to this element and in
turn, produces a vacancy in
the M or N shell.
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9. “Auger” Electron
The excitation energy
from the inner atom
is transferred to one of
the outer electrons
causing it to be ejected
from the atom.
This process is a
competing process to the
XRF.
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10. • X-ray fluorescence's spectroscopy provides a means of
identification of an element, by measurement of its
characteristic X-remission length or energy
• The method allows the quantification of a given element
by first measuring the emitted characteristic line intensity
and then relating this intensity to elemental concentration
• The energy of the peaks leads to the identification of the
elements present in the sample (qualitative analysis),
• while the peak intensity provides the relevant or absolute
elemental concentration (semi-quantitative or quantitative
analysis).
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11. Advantages of XRF Analysis :-
• Rapid analysis
• Nondestructive analysis
• No spectrum is affected by chemical bonding
• Easily analysis of the element among the same family elements
• High accurate analysis
• Easy qualitative analysis
• Easy sample preparation
• Elemental oxygen can be analyzed but oxides content is estimated
by assuming the sample contains certain oxides.
• Consequently oxides content is estimated result because XRF can
only determine elements.
• Elemental carbon and sulfur can also be analyzed .
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12. Schematic figure of an x-ray fluorescence
spectrophotometer
 sin.2dn BASIC PRINCIPLE:
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13. X-ray
generator
Sample
chamber
collimator
Analyzing
crystal
collimator
To counting and
recording part
To
spectrometer
part
X-ray generator part
Spectrometer Part
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14. • X-ray tube for XRF spectrometer is a diode (vacuum tube)
consist of the filament generating thermo- electron and the
anode (target) generating x-rays.
• Near the target, there is a window to pass x-rays through to the
outside tube. The window material, Beryllium, is employed
because of its nature for having the excellent transmission
(penetration) of x-rays.
• There two types of x-ray tubes:
- Side Window Type X-ray Tube
- End Window Type X-ray Tube
X-RAY GENERATOR
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15. Structure of X-Ray tubes
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16. • Rh target end-window type x-ray tube has the features that
since it is effectively sensitive to the element less than the
atomic number 16 (S) and it can also obtain relatively the good
sensitivity to the heavy elements. It can make the
measurements from heavy elements to light elements without
exchanging X-tube.
• The frequency of using this Rh target X-ray tube is high
• In case of side window type x-ray tube, the W and Mo target
x-ray tubes will be applied for the analysis of heavy elements
and the Cr target x-ray tube will be applied for the analysis of
light elements.
• Especially , the Mo target x-ray tube will be frequently applied
for the analysis of environmental pollution such as Hg, Pb, As
and so on.
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17. Analyzing crystal
• The diffraction phenomenon of x-ray through the single crystal is
utilized for the dispersion of x-rays. This crystal is called the
analyzing crystal. In accordance with the wavelength region of the
fluorescence x-rays, the optimum analyzing crystal is employed
respectively.
• Analyzing crystals such as TAP, RAP, ADP, EDDT, PET, NaCl etc.
are sensitive to humidity. If they are left in the air, their surface will
deliquesce, leading to lower x-ray reflection intensities and
deteriorated resolution. It is therefore necessary to keep the interior
of the spectroscopic chamber in a vacuum even during the time that
the x-ray spectrometer is not used.
• Samples which are highly acid or alkaline, or which will sublime at
low temperatures will deteriorate analyzing crystal leading to lower
reflection intensities.
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18. • The fluorescence x-ray excited from the specimen are
diffracted through the analyzing crystal by scanning
goniometer.
• The diffracted x-rays are detected by the counter and through
the electronic circuit, the intensities are recorded automatically
on the charge recorder.
• The characteristic wavelength (λ) emitted by each element in
the sample is analyzed by applying a diffracting (an analyzing)
crystal which has a certain d value.
• Diffracting angles (θ) are measured and λ of each element is
determined using Bragg’s law.
• By determining the elemental spectra recorded on a chart, we
can learn the name of elements containing in the specimen.
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19. Fluorescent spectrum recording of a stainless steel
Example of a qualitative measurement result
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20. • The primary radiation was supplied by tungsten-target tube operated at 50
kV, and the sample was stainless steel containing 18%Cr and 8% Ni.
• The K lines of all the major constituents (Fe, Cr and Ni) and of some of the
minor constituents (Mn and Co) are apparent.
• In addition tungsten L lines can be seen; these always be present when a
tungsten tube is used. The copper K lines are due to copper existing as an
impurity in the tungsten target
Consider the quantitative analysis result of a dry limestone sample which is obtained
from XRF analysis
ELEMENT SPECTRUM WT%
Mg Mg Kα 1.2
Ca Ca Kα 90.0
Fe Fe Kα 2.3
Si Si Kα 6.5
* Mg and Ca are found as carbonates,
while Fe and Si as oxides. Convert the
data to mol % of the actual substances
(CaCO3, MgCO3, Fe2O3 and SiO2)
present in the limestone. Mol weight :
Ca = 40.1; Mg = 24.3; C = 12.0; O =
16.0 and Fe = 55.8, Si=28.1.
* Spectra of oxygen and carbon are not
considered.
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21. Quantitative Analysis
Concentration
•XRF is a reference method,
standards are required for
quantitative results.
•Standards are analysed, intensities
obtained, and a calibration plot is
generated (intensities vs.
concentration).
• XRF instruments compare the
spectral intensities of unknown
samples to those of known standards.
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22. XRF Application
During the last decades, the development in X-ray detectors has
established the XRF method as a powerful technique in a number
application fields, including:
• Ecology and environmental management: measurement of
heavy metals in soils, sediments, water and aerosols
• Geology and mineralogy: qualitative and quantitative analysis
of soils, minerals, rocks etc.
• Metallurgy and chemical industry: quality control of raw
materials, production processes and final products
• Paint industry: analysis of lead-based paints
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23. • Jewelry: measurement of precious metals concentrations
• Fuel industry: monitoring the amount of contaminants in fuels
• Food chemistry: determination of toxic metals in foodstuffs
• Agriculture: trace metals analysis in soils and agricultural
products
• Archaeology
• Art Sciences: study of paintings, sculptures etc.
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