This document discusses X-ray fluorescence (XRF), a technique used to analyze the chemical composition of materials. XRF works by exciting a sample with an X-ray source, which causes fluorescent X-rays to be emitted from the sample that are characteristic of its elemental composition. The document covers the basic principles of XRF, how it is used to generate spectra to analyze samples, common instrumentation including X-ray sources and detectors, sample preparation methods, applications in fields like mining and environmental analysis, and limitations of the technique.

1. Adarsh Dubey
Iph150012012
Advance experimental technique
X-RAY FLUORESECENCE

2. CONTENTS
• DEFERENCETO X-RAYS
• GENERATING X-RAYS
• GENERATING SECONDARY X-RAYS
• THEORY & PRINCIPLE
• INSTRUMENTATION
• SAMPLE PREPRATION
• ANALYSIS OF SAMPLE
• APPLICATION
• LIMITATION

3. DEFERENCE:
X-rays were discovered by Wilhelm Roentgen
X-ray region 0.1to100 A˚
The penetrating power of x-rays depends on energy also, there are two
types of x-rays.
i) Hard x-rays: which have high frequency and have more energy.
ii) soft x-rays: which have less penetrating and have low energy

4. GENERATION OF X-RAYS
X-rays can be generated by decelerating electrons.
X-rays are generated by bombarding a target with an
electron beam.
Beam of electrons
Target
X-rays
BLOCK DIAGRAM OF XRAY PRODUCTION

5. Be Window
Silicone Insulation
Glass Envelope
Filament
Electron beam
Target (Ti, Ag,
Rh, etc.)
Copper Anode
HV Lead
XRAY PRODUCTION INSTRUMENT

6. L Shell
K Shell
K alpha
K beta
M Shell
L alpha
N Shell
L beta
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.

7. GENERATION OF SECONDARY X-RAYS
1) An electron in the K shell is ejected from
the atom by an external primary excitation
x-ray, creating a vacancy.
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.
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.

8. THEORY & PRINCIPLE
• XRF works on methods involving interactions between electron
beams and x-rays with samples.
• Made possible by the behaviour of atoms when they interact
with radiation.
• When materials are excited with high-energy, short wavelength
radiation (e.g., X-rays), they can become ionized.
• If the energy of the radiation is sufficient to dislodge a tightly-
held inner electron, the atom becomes unstable and an outer
electron replaces the missing inner electron.
• When this happens, energy is released due to the decreased
binding energy of the inner electron orbital compared with an
outer one.

9. •XRF is a reference method, standards are required for quantitative
results.
•Standards are analysed
• Intensities obtained
• Calibration plot is generated (intensities vs. concentration).
• XRF instruments compare the spectral intensities of unknown
samples to those of known standards.

10. • The emitted radiation is of lower energy than the primary
incident X-rays and is termed fluorescent radiation.
• Because the energy of the emitted photon is characteristic of a
transition between specific electron orbitals in a particular
element, the resulting fluorescent X-rays can be used to detect
the abundances of elements that are present in the sample.
 sin.2dn BASIC PRINCIPLE:

11. INSTRUMENTATION
Basic instrumentation

12. TWO DIFFERENT KIND OF XRF
Wavelength Dispersive WDXRF Spectrometer
Energy Dispersive EDXRF Spectrometer

13. Collimators
Collimators are usually circular or a slit and restrict the size or
shape of the source beam for exciting small areas in either
EDXRF or WDXRF instruments..
Sample
Tube

14. Source Filters
Filters perform one of two functions
Background Reduction
Improved Fluorescence
Detector
X-Ray
Source
Source Filter

15. Secondary Targets
Sample
X-Ray Tube
Detector
Secondary Target
1.The x-ray tube excites the secondary target.
2.The secondary target fluoresces and excites the sample.
3.The detector detects x-rays from the sample.

16. Detectors
 Si(Li) -EDXRF
 PIN Diode-EDXRF
 Silicon Drift Detectors-EDXRF
 Proportional Counters-WDXRF
 Scintillation Detectors-WDXRF

17. PN-Detector Principles
2
E
n
e
n = number of electron-hole pairs produced
E = X-ray photon energy
e = 3.8ev for Si at LN temper
where :
atures

A detector is composed of a non-conducting or semi-conducting material
between two charged electrodes.
X-ray radiation ionizes the detector material causing it to become conductive,
momentarily.
The newly freed electrons are accelerated toward the detector anode to produce
an output pulse.
An ionized semiconductor produces electron-hole pairs, the number of pairs
produced is proportional to the X-ray photon energy.

18. SAMPLE PREPRATION
Powders:
 Grinding (<400 mesh if possible) can minimise scatter affects due to
particle size.
 Pressing (hydraulically or manually) compacts more of the sample into the
analysis area, and ensures uniform density and better reproducibility.
Solids:
 Orient surface patterns in same manner so as minimise scatter affects.
 Polishing surfaces will also minimise scatter affects.
 Flat samples are optimal for quantitative results.
Liquids:
 Samples should be fresh when analysed and analysed with short analysis
time - if sample is evaporative.
 Sample should not stratify during analysis.
 Sample should not contain precipitants/solids, analysis could show settling
trends with time.

19. ANALYSIS OF SAMPLE
Fluorescent spectrum recording of a stainless steel
The sample was stainless steel containing 18%Cr and 8% Ni.

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
• 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.

21. APPLICATION
X-Ray fluorescence is used in a wide range of applications, including
• research in igneous, sedimentary, and metamorphic petrology
• soil surveys
• mining (e.g., measuring the grade of ore)
• cement production
• ceramic and glass manufacturing
• metallurgy (e.g., quality control)
• environmental studies (e.g., analyses of particulate matter on air filters)

22. LIMITATION
• In practice, most commercially available instruments are very limited in
their ability to precisely and accurately measure the abundances of elements
with Z<11 in most natural earth materials.
• XRF analyses cannot distinguish variations among isotopes of an element,
so these analyses are routinely done with other instruments.
• XRF analyses cannot distinguish ions of the same element in different
valence states, so these analyses of rocks and minerals are done with
techniques such as wet chemical analysis or Mossbauer spectroscopy.
• relatively large samples, typically > 1 gram
• materials that can be prepared in powder form and effectively
homogenized
• materials for which compositionally similar, well-characterized standards
are available
• materials containing high abundances of elements for which absorption and
fluorescence effects are reasonably well understood