In mineral science, there are several analytical instruments used for various purpose, viz… Scanning electron microscopy X-ray diffraction Transmission electron microscopy X-ray fluorescence Flame atomic absorption spectroscopy Electron microprobe analysis Secondary ion mass spectrometry Atomic force microscopy

1. ANALYTICAL
INSTRUMENT
Presented by :- Pranjit Sharmah
2013-2014
M.Sc Sem I

2. ANALYTICAL
INSTRUMENTS
In mineral science, there are several analytical
instruments used for various purpose, viz…
 Scanning electron microscopy
 X-ray diffraction
 Transmission electron microscopy
 X-ray fluorescence
 Flame atomic absorption spectroscopy
 Electron microprobe analysis
 Secondary ion mass spectrometry
 Atomic force microscopy 2

3. SCANNING ELECTRON MICROSCOPY (SEM)
The scanning electron microscope has an electron
optical column in which a finely focused electron beam
can be scanned over a specified area of the specimen.
3

4. FUNDAMENTAL PRINCIPLES OF SCANNING
ELECTRON MICROSCOPY (SEM)
Accelerated electrons in an SEM carry significant
amounts of kinetic energy, and this energy is
dissipated as a variety of signals produced by
electron-sample interactions when the incident
electrons are decelerated in the solid sample. These
signals include secondary electrons (that produce
SEM images), backscattered electrons (BSE),
diffracted backscattered electrons (EBSD) that are
used to determine crystal structures and
orientations of minerals.
4

5. SCHEMATIC DRAWING OF FINELY FOCUS ELECTRON
BEAM IMPINGING ON A MATERIAL SURFACE :
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6. APPLICATIONS OF SEM
The SEM is routinely used to –
 To generate high-resolution images of shapes of objects.
 Identify phases based on qualitative chemical analysis
and/or crystalline structure.
 SEMs equipped with diffracted backscattered electron
detectors can be used to examine microfabric and
crystallographic orientation in many materials.
6

7. STRENGTHS AND LIMITATIONS OF SEM
Strength:-
 Most SEM are comparatively easy to operate.
 Modern SEMs generate data in digital format which are highly
portable.
 For many applications, data acquisition is rapid.
Limitations-
 . Samples must be solid and they must fit into the microscope
chamber
 An electrically conductive coating must be applied to electrically
insulating samples for study in conventional SEM. 7

8. X-RAY DIFFRACTION TECHNIQUES (XRD)
The first application of an X-ray experiment to
the study of crystalline material in 1912 by
Max Von Lou. There are two different X-ray
diffraction techniques –
i) Single crystal techniques
ii)X-ray powder diffraction techniques
8

9. SINGLE CRYSTAL TECHNIQUES……
What is Single-crystal X-ray Diffraction???
Single-crystal X-ray Diffraction is a non-destructive
analytical technique which provides detailed
information about the internal lattice of crystalline
substances, including unit cell dimensions, bond-lengths,
bond-angles, and details of site-ordering.
9

10. FUNDAMENTAL PRINCIPLES OF SINGLE-CRYSTAL X-RAY
DIFFRACTION
Single crystal X-ray diffraction concern with the interaction of an
X-ray beam with a very small single crystal.
The X-ray beam and the crystalline structure produce that can be
recorded on film or measured by electronic device called X-ray
counter.
The most commonly used single crystal method is precession
method.
The modern approach to data acquisition by “single crystal
diffractometer” .
The most commonly used automated technique in structure analysis
is four circle diffractometer. 10

11. APPLICATIONS
Specific applications of single-crystal diffraction include:
 For precise determination of a unit cell, including cell
dimensions and positions of atoms within the lattice.
 New mineral identification, crystal solution and
refinement.
 Determination of crystal-chemical vs. environmental
control on mineral chemistry etc.
11

12. STRENGTHS AND LIMITATIONS OF SINGLE-CRYSTAL
X-RAY DIFFRACTION
Strengths:-
 Non-destructive.
 Detailed crystal structure, including unit cell dimensions, bond-lengths,
bond-angles and site-ordering information
Limitations
 Must have a single, stable sample, generally between 50—250
microns in size.
 Optically clear sample.
 Data collection generally requires between 24 and 72 hours 12

13. X-RAY POWDER DIFFRACTION (XRD)
X-ray powder diffraction (XRD) is a rapid analytical
technique primarily used for phase identification of a
crystalline material.
13

14. FUNDAMENTAL PRINCIPLES OF X-RAY POWDER
DIFFRACTION (XRD)
The sample of powder diffrractometer analysis spread uniformly
over a surface of a glass slide. The instrument is so constructed that
the sample, when clamped in place, rotates in the path of a
collimated X-ray beam, an X-ray detector, mounted on a arm
rotates about it to pick up the diffracted X-ray signals. X-ray
detector maintains the appropriate geometrical relationship to
receive each diffraction separately. Once the diffractometer tracing
is obtained and various diffraction peaks have been tabulated in
sequence of decreasing interplanar spacing together with their
relative intensities.
14

15. SCHEMATIC ILLUSTRATION OF A SINGLE-CRYSTAL
DIFFRACTOMETER
15

16. APPLICATIONS
X-ray powder diffraction is most widely used for:-
 Characterization of crystalline materials
 Identification of fine-grained minerals that are
difficult to determine optically.
 Measurement of sample purity.
16

17. STRENGTHS AND LIMITATIONS OF X-RAY POWDER
DIFFRACTION (XRD)?
Strength :-
 Powerful and rapid (< 20 min) technique for
identification of an unknown mineral.
 Minimal sample preparation is required.
Limitation :-
 Requires tenths of a gram of material which must be
ground into a powder.
 For mixed materials, detection limit is ~ 2% of sample
 For unit cell determinations, indexing of patterns for
non-isometric crystal systems is complicated.
17

18. X-RAY FLUORESCENCE(XRF)
An X-ray fluorescence (XRF) spectrometer is an x-ray
instrument used for routine, relatively non-destructive
chemical analyses of rocks, minerals, sediments and fluids.
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19. FUNDAMENTAL PRINCIPLES OF X-RAY FLUORESCENCE
(XRF)
An XRF spectrometer works if a sample is illuminated by
an intense X-ray beam, known as the incident beam, some
of the energy is scattered, but some is also absorbed within
the sample in a manner that depends on its chemistry.
When the primary X-ray beam illuminates the sample,
excited sample in turn emits X-rays along a spectrum of
wavelengths characteristic of the types of atoms present in
the sample. Various types of detector are used to measure
the intensity of the emitted beam. The intensity of the
energy measured by these detectors is proportional to the
abundance of the element in the sample. 19

20. SCHEMATIC CROSS SECTION OF XRF
20

21. APPLICATION
X-Ray fluorescence is used in a wide range of
applications, including:-
 Research in igneous, sedimentary, and
metamorphic petrology
 Mining (e.g., measuring the grade of ore)
 Metallurgy (e.g., quality control)
21

22. STRENGTHS AND LIMITATIONS……..
Strengths:-
 Bulk chemical analyses of major elements (Si, Ti, Al, Fe,
Mn, Mg, Ca, Na, K, P) in rock and sediment.
Limitations:-
 XRF analyses cannot distinguish variations among isotopes
of an element.
22

23. ELECTRON MICROPROBE ANALYSIS(EMPA)
An electron probe micro-analyzer is a micro beam instrument used
primarily for thein situ non-destructive chemical analysis of minute
solid samples. EPMA is also informally called an electron microprobe,
or just probe. It is fundamentally the same as an SEM, with the added
capability of chemical analysis.
23

24. FUNDAMENTAL PRINCIPLES OF ELECTRON PROBE
MICRO-ANALYZER (EMPA)
An electron microprobe operates under the principle that if a solid
material is bombarded by an accelerated and focused electron
beam, the incident electron beam has sufficient energy to liberate
both matter and energy from the sample. These electron-sample
interactions mainly liberate heat, but they also yield both
derivative electrons and x-rays. These quantized x-rays are
characteristic of the element. EPMA analysis is considered to be
"non-destructive" so it is possible to re-analyze the same materials
more than one time.
24

25. APPLICATIONS OF EMPA
 Quantitative EMPA analysis is the most commonly used
method for chemical analysis of geological materials at
small scale.
 EPMA is also widely used for analysis of synthetic
materials such as optical wafers, thin films,
microcircuits, semi-conductors, and superconducting
ceramics.
25

26. STRENGTHS AND LIMITATIONS OF ELECTRON
PROBE MICRO-ANALYZER (EPMA)
Strength's:-
 An electron probe is the primary tool for chemical analysis of solid
materials at small spatial scales .
 Spot chemical analyses can be obtained in situ , which allows the
user to detect even small compositional variations within textural
context or within chemically zoned materials.
Limitations:-
 Electron probe unable to detect the lightest elements (H, He and Li).
 Probe analysis also cannot distinguish between the different
valence states of Fe. 26

27. TRANSMISSION ELECTRON MICROSCOPY
(TEM)
Transmission electron microscopy (TEM) is
a microscopy technique in which a beam of electrons is
transmitted through an ultra-thin specimen, interacting
with the specimen as it passes through.
27

28. FUNDAMENTAL PRINCIPLES OF TEM
A transmissions electron microscope consist of a finely focused
electron beam that impinges on a very thin foil of an object.
Transmission through the object, can be used to display electron
diffraction patterns, and high resolution transmission electron
microscope images. The thin foil is produced by ion bombardment
or sputter-etching method for non conducting materials and
conducting material is done by electrochemical methods. The thin
foil is held n place with a sample holder centered in a electron
beam.
28

29. APPLICATIONS OF TEM
Transmission electron microscope provide information
about symmetry, distance among indexed diffraction
provide information about unit cell size. This in turns
allows for phase identification.
29

30. STRENGTHS AND LIMITATIONS OF TEM
Strength:-
 The TEM technique is especially powerful in elucidating structural
features that range in size from 100 to 10,000 Ao .
 TEM studies allow for phase identification of extremely small
particles or intergrowths of minerals.
Limitation:-
 TEMs are large and very expensive.
 TEMs require special housing and maintenance.
 Images are black and white. 30

31. FLAME ATOMIC ABSORPTION MICROSCOPY
This analytical technique is commonly considered a “wet” analytical
procedure because the original sample must be completely
dissolved in a solution before it can be analysed.
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32. FUNDAMENTAL PRINCIPLES OF FAA
The energy source in this technique is a light source. When the light
energy is equivalent to the energy required to raise the atom from
its low energy level to high energy levels, it is absorbed and causes
excitation of atom. In order to determine element concentrations by
this method, the atoms must be completely free of any of the
bonding. The amount of light radiation that is measured by
spectrometer is expressed by –
A= log lo
/ l, where A is absorbance, l0 is the
incident light intensity and l the transmitted light intensity.
The incident light intensity is supplied by hollow cathode
lamp. The reduction in intensity is measured by the photomutiplier.
32

33. STRENGTH AND LIMITATION OF FAA
Strength:-
 Greater sensitivity and detection limits than other methods.
 Direct analysis of some types of liquid samples.
 Very small sample size.
Limitation:-
 The method cannot be used to detect non-metallic elements.
 It also suffers from ionic interference.
33

34. SECONDARY ION MASS SPECTROMETRY(SIMS)
Secondary ion mass spectrometry (SIMS) is a technique
used to analyse the composition of solid surfaces
and thin films by sputtering the surface of the specimen
with a focused primary ion beam.
34

35. FUNDAMENTAL PRINCIPLE OF SIMS
The instruments employs a focused beam of ions that impinges on
the solid surface of the sample. These atoms of the surface are
extracted as secondary ions for analysis by mass spectrometer. In
this method particles are ejected in ionized state. The instruments
consists of a source of bombarding primary ions that are focused
onto the specimen sample by lens systems. In most of the
instruments used for mineralogical analysis the extracted
secondary ions focused into a double focusing mass spectrometer
which separates ions on the basis of energy and mass.
35

36. SCHEMATIC DEPICTION OF SIMS SOURCE
36

37. APPLICATIONS OF SIMS
 It is commonly applied to the determination of the abundance and
distribution of the rare earth material.
 The SIMS technique also allows collecting isotropic composition
for age dating and diffusion studies.
 Instrument can be used to determine the concentration of any
chemical element.
37

38. STRENGTH AND LIMITATIONS OF SIMS
Strength :-
 This technique offers very high sensitive quantitative elemental
analysis with detection limits in the parts per million to parts per
billion range.
 It can analyze most chemical elements from H to U.
Limitations:-
 Not all elements in all substrates (matrices) can be
analysed quantitatively.
 SIMS instrumentation tends be expensive. 38

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