DiffractometerA diffractometer (pronunciation: di-"frak-'tä-m&-t&r) is a measuringinstrument for analyzing the structure of a material fromthe scattering pattern produced when a beam of radiation or particles(such as X-rays or neutrons) interacts with it.

Bruker X8 Apex diffractometer at the University of Arizona

Department of Geosciences

X-ray powder diffraction is one of the most potential

characterization tools and a nondestructive technique for

characterizing both organic and inorganic crystalline materials.

The method previously used for measuring

phase identification,

quantitative analysis and

to determine structure imperfections of samples

WHAT IS X-RAY DIFFRACTION ?

• The periodic lattice found in crystalline structure may act as diffraction grating

for wave particles of electromagnetic radiation with wavelength of a similar

order of magnitude (1Aº).

• The atomic planes of a crystal causes an incident beam of X-rays to interfere

with one another as they come out from the crystal. This phenomenon is

called X-ray diffraction.

XRD PRINCIPLE:

X-ray diffraction is based on constructive interferenceof monochromatic x-rays and a crystalline sample. These x-raysare generated by a cathode ray tube, filtered to producemonochromatic radiation ,collimated to concentrate and directedtowards the sample. The interaction of incident rays with thesample produces constructive interference when conditionssatisfy Bragg’s law.

3

Working:

• The technique of single-crystal X-ray crystallography has three basic steps. The first—and often most difficult—step is to obtain an adequate crystal of the material under study. The crystal should be sufficiently large (typically larger than 0.1 mm in all dimensions), pure in composition and regular in structure, with no significant internal imperfections such as cracks or twinning.

• In the second step, the crystal is placed in an intense beam of X-rays, usually of a single wavelength (monochromatic X-rays), producing the regular pattern of reflections. As the crystal is gradually rotated, previous reflections disappear and new ones appear; the intensity of every spot is recorded at every orientation of the crystal. Multiple data sets may have to be collected, with each set covering slightly more than half a full rotation of the crystal and typically containing tens of thousands of reflections.

• In the third step, these data are combined computationally with complementary chemical information to produce and refine a model of the arrangement of atoms within the crystal. The final, refined model of the atomic arrangement—now called a crystal structure—is usually stored in a public database.

X-ray Tube: the source of X rays

Incident-beam optics: condition the X-

ray beam before it hits the sample

The goniometer: the platform that

holds and moves the sample, and

detector.

The sample & sample holder

Receiving-side optics: condition the X-

ray beam after it has encountered the

sample

Detector: count the number of X rays

scattered by the sample

ESSENTIAL PARTS OF THE DIFFRACTOMETER

Schematic diagram of an

x-ray diffractometer; T x-ray source,

S specimen, C detector, and

O the axis around which the

specimen and detector rotate

SAMPLE PREPARATION FOR XRD

An ideal powder sample should have many crystallites in

random orientations

If the crystallites in a sample are very large, there will not be a

smooth distribution of crystal orientations. You will not get a

powder average diffraction pattern.

Crystallites should be <10 mm in size to get good powder

statistics

Large crystallite sizes and non-random crystallite orientations

both lead to peak intensity variation.

X-RAY DIFFRACTION PATTERN OF AMORPHOUS SOLIDS

Dried ZrO2

Ceria

CERIA ZrO2

XRD PATTERNS OF NANO-PARTICLES

DIFFRACTION PATTERN OF A SINGLE CRYSTAL

A single crystal will produce only one family of peaks

in the diffraction pattern

INTE

NSI

TY

DIFFRACTION PATTERN OF A POLYCRYSTALLINE SAMPLE

INTE

NSI

TY

A polycrystalline samples contain thousands of crystallites, therefore all possible diffraction peaks should be observed.

EXTINCTION RULES FOR CUBIC CRYSTALS

Bravais Lattice Allowed Reflections

SC All

BCC (h + k + l) even

FCC h, k and l unmixed

DC

h, k and l are all oddOr

all are even& (h + k + l) divisible by 4

h2 + k2 + l2 SC BCC FCC DC

1 100

2 110 110

3 111 111 111

4 200 200 200

5 210

6 211 211

7

8 220 220 220 220

9 300, 221

10 310 310

11 311 311 311

12 222 222 222

13 320

14 321 321

Type of information obtain by XRD analysis

- The kinds of materials that compose a solid (Qualitative analysis).

- The quantity of materials that compose the solid (Quantitative

analysis).

- The quantity of materials that are crystallized (crystallinity).

- The amount of stress present in the solid (residual stress).

- The size of crystallites that compose the solid (crystallite size).

- Average orientation of crystallites that compose the solids (texture).

APPLICATIONS OF XRD1. Structure of crystals

2. Polymer characterisation

3. State of anneal in metals

4. Particle size determination

a) Spot counting method

b) Broadening of diffraction lines

c) Low-angle scattering

5.Applications of diffraction methods to complexes

a) Determination of cis-trans isomerism

b) Determination of linkage isomerism

6.Miscellaneous applications

APPLICATIONS OF XRD

XRD is a nondestructive technique

To identify crystalline phases and orientation

To determine structural properties: strain, grain size, epitaxy, phase

composition, preferred orientation, order-disorder transformation,

thermal expansion

To measure thickness of thin films and multilayers

To determine atomic arrangement

Detection limits: ~ 3% in a two phase mixture; can be ~ 0.1 % with

synchrotron radiation

Companies and manufacturers of XRD

Agilent Technologies.

Agilent Technologies manufactures X-ray crystallography instruments (XRD, X-ray diffractometer system).

Analytical X-Ray Systems (AXRS).

Analytical X-Ray Systems Co. Ltd. is the official representative of PANalytica

B.V. (Netherlands) in Russia. PANalytical (formerly Philips Analytical) is one of the leading

manufacturers of X-ray diffractometry and X-ray fluorescence spectrometry instrumentation

worldwide

Other companies includeAnton Paar GmbH.

Bourevestnik.

Bourevestnik (St. Petersburg, Russia) is a manufacturer of X-ray diffraction and X-ray spectroscopy instruments

Bruker Corporation.

Bruker is a manufacturer of X-ray diffractometers

Companies and manufacturers of XRD

GBC Scientific Equipment Pty Ltd.

INEL.

Innov-X Systems, Inc.

Jordan Valley Semiconductors Ltd.

MOXTEK Inc.

Rigaku Corporation.

Scientific Instruments (Научные Приборы).

Shimadzu Corporation.

Bruker D8 X-ray diffractometers

• The Bruker D8 X-ray diffractometers are designed to easily accommodate all X-ray diffraction applications in material research, powder diffraction and high resolution diffraction. All new D8 goniometer are equipped with stepper motors with optical encoder to ensure extremely precise angular values. The D8 X-ray diffractometer can be used for nearly all X-ray diffraction application, such as structure determination, phase analysis, stress and texture measurement.

Bruker's X-ray Diffraction D8-Discover instrument

Phillips X’pert MPD Diffractometer

The Phillips X’pert MPD Diffractometer is a versatile instrument that is designed be used in many X-ray data collection applications.

Interchangeable elements of the instrument allow for multiple types of data collection and sample types to be accommodated.

PANalytical’s X-ray diffractometers

PANalytical’s X-ray diffractometers are designed for obtaining the ultimate quality diffraction data, combined with ease of use and flexibility to quickly switch to different applications.

X’Pert³ MRD

The standard research and development version for use with thin film samples, wafers (complete mapping up to 100 mm) and solid materials. High-resolution analysis capability is improved by the outstanding accuracy of a new high-resolution goniometer using Heidenhain encoders.

X'Pert³ MRD XL

The X'Pert³ MRD XL meets all the high-resolution XRD analysis requirements of the semiconductors, thin films, and advanced materials industries. Complete wafer mapping up to 200 mm is possible. The X’Pert3 version comes with longest liftetime of incident beam components (CRISP) and maximum uptime with pneumatic shutters and beam attenuators.

By facilitating analysis of wafers of up to 300 mm in diameter, with a sophisticated, automatic wafer loader option, the X'Pert³ MRD XL becomes an advanced tool for quality control of industrial thin layered structures.

X'Pert³ MRD XL

• From nanomaterials to bulk samplesThe X’Pert³ MRD systems handle the same wide range of applications, and

are especially suitable for thin film analysis applications such as rocking curve analysis and reciprocal space mapping, reflectometry, thin film phase analysis and residual stress and texture analysis.

XRD at NUST (SCME)

• XRD machine at SCME

Make ( Stoe, Germany )

Model ( Theta-Theta )

The STOE Theta/theta X-ray Diffractometer System is a multi-purpose instrument which combines the advantages of the Theta/theta-arrangement of X-ray tube and counter with a flexible choice of beam geometry, sample holders and other attachments.

Instrument Features •2theta range from -10° to 168°

•Measuring circle of 270 mm radius

•Tube translation for optimal primary beam intensity

•All possible scan modes:

(theta/2theta, omega, 2theta, 2theta:theta variable)

•Adjusting kit for optimal alignment

•Sample maintained in horizontal position

•Highest reproducibility

•Precision slit system

•Soller slits

•Sample holder with variable rotation speed

•All optional devices are easily adaptable

•FWHM down to delta 2theta=0.025°

•Multi-purpose instrument

STOE Theta/theta X-ray Diffractometer System

Advantages

• XRD isthe least expensive, the most convenient & the most widely used method to determine crystal structures.

• XRD Techniques give information about the structure of solids, the arrangement of the

atoms that compose the solid.

• XRD permits nondestructive structure analyses

Disadvantages• XRD has size limitations. It is much more accurate for measuring large crystalline

structures rather than small ones. Small structures that are present only in trace amounts will often go undetected by XRD readings, which can result in skewed results.

• X-Rays do not interact very strongly with lighter elements.

• It is relatively low in sensitivity.

Different research groups /universities

• Safinya Group Research: X-Ray Scattering / Diffraction

(Stanford Synchrotron Radiation Laboratory)

• Maxwell Powder XRD Facility - Dutton Research Group

(University of Cambridge)

The Maxwell Centre houses a Bruker D8 Advance powder X-ray diffractometer. The instrument is suitable for both short measurements to determine phase purity and longer scans for quantitative structural analysis.

• National Centre for Earth Science Studies(INDIA)

The XRD facility at NCESS, commissioned in 2006, consists of a PANalytical 3 kW X’pert PRO X-ray diffractometer

Universite de Montreal

(Microstar system –X8 proteum)

University of Southampton

(Rigaku FR-E+ Single Crystal X-Ray Diffractometer)

Imperial College London

(The facility is currently equipped with 2 PANalytical MRDs, 2 PANalytical MPDs and a Bruker D2 desk-top instrument)

Takamura Research Group

(Bruker D8 Discover Diffractometer System)

References

• https://en.wikipedia.org/wiki/X-ray_crystallography

• http://www.imperial.ac.uk/materials/eqpmt/xrd/

• http://research.engineering.ucdavis.edu/takamura/equipment/

• http://www.esc.cam.ac.uk/resources/facilities/equipment-and-instruments/XRD/xrd-current-equipment

• https://www.slideshare.net/gopinathkarnam/x-ray-diffraction-25472126