XRD: STRUCTURAL ANALYSIS AT LIST

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• Yves Fleming

• Jérôme Bour

• Introduction to structure and structural analysis

• XRD facilities at LIST

• Examples:

• Powder analysis

• Thin film analysis

• Phase identification

• Phase transformations

• Stress analysis

• Texture analysis and pole figures

• X-Ray reflectometry

• SAXS / WAXS

• Further developments

Outline

OVERVIEW

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Crystalline versus amorphous structure: SiO2 example

STRUCTURE

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• The crystal structure describes the atomic arrangement of a material.

• When the atoms are arranged differently, a different diffraction pattern is

produced (ie. glass vs. cristobalite)

Quartz Cristobalite Glass

Information from diffraction spectra: SiO2 Example

STRUCTURE

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• These three phases of SiO2 are chemically identical

• The amorphous glass does not have long-range atomic order and therefore produces only broad scattering peaks

• Quartz and cristobalite have two different crystal structures • The Si and O atoms are arranged differently

• Both have structures with long-range atomic order

• The difference in their crystal structure is reflected in their different diffraction patterns

Position [°2Theta] (Copper (Cu)) 20 30 40 50

Counts

0

2000

4000

0 1000

2000

3000

4000

0

2000

4000

SiO2 Glass

Quartz

Cristobalite

• Cu Kα (and Mo Kα) X-ray sources

• Parallel beam configuration (Göbbel mirror)

• Point/line focused beam capabilities

• Energy Sensitive Detector and scintillator

• Eulerian cradle

• Hot stage

• Mainly used for :

• Grazing incidence analysis

• Phase identification

• Rocking curves

• X-Ray reflectometry

• Residual stress analysis

• Texture analysis

Bruker D8 Discovery

Bruker D8 Discovery

INSTRUMENTS AVAILABLE @ LIST

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• Cu Kα X-ray source

• Parallel beam as well as parafocusing beam configurations

• Possibility to use programmable slits

• Transmission configuration • Small Angle X-Ray scattering (SAXS)

• Wide Angle X-Ray scattering (WAXS)

• Point/line focused beam capabilities

• 1D-Position Sensitive Detector

• Cryo-stage and hot stage

• Rel. Humidity chamber

• Mainly used for: • Powder analysis

• Phase identification

• X-Ray reflectometry

• Semi-quantitative as well as quantitative phase analysis

Panalytical X’Pert Pro

Panalytical X’Pert Pro

INSTRUMENTS AVAILABLE @ LIST

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Classical Reflection

ANALYSIS OF POWDERS

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• The incident angle, w, is defined between the X-ray source and the sample.

• The diffraction angle, 2q, is defined between the incident beam and the detector.

• In the Bragg-Brentano geometry, the diffraction vector (s) is always normal to the sample surface.

s

Powder diffraction

ANALYSIS OF POWDERS

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2q 2q 2q

For every set of planes, there will be a small percentage of crystallites that are properly

oriented to diffract

Basic assumptions of powder diffraction:

For every set of planes, there is an equal number of crystallites that will diffract

There is a statistically relevant number of crystallites

s

[100] [110]

s s

[200]

Grazing Incidence

THIN FILM ANALYSIS

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ωi=0.5º: top layer ωi=3º

Substrate (blue index)

XRD pattern of a bilayered coating on WC substrate (V. Hody)

ωi

WC substrate

coating 2θ

fixed

BF-TEM image TiAlTaN

900 ºC (6 hrs)

200 nm

Crystalline coating

A larger incidence angle ωi increases penetration depth Characterisation of thin films using XRD is possible

Temperature chambers

ANALYSIS OF PHASE TRANSFORMATIONS

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• Hot stage characteristics:

• From room temp. up to 1100°C

• Vacuum (down to 10-2 mbar)

• Controlled atmosphere

(inert gas: H2, N2, Ar)

• Temperature chamber characteristics:

• -193°C up to 450°C ( in vacuum)

• Ambient up to 300°C (in controlled atm.)

• Rel. humidity generator:

• between 5% and 90 % at 25°C

Phase transformations in thin films

ANALYSIS OF PHASE TRANSFORMATIONS

11 V. Khetan et al., ACS Appl. Mater. Interfaces 2014, 6, 4115−4125

• X-ray diffraction spectra of an Al0.48Ti0.4Ta0.12N hard

coating.

• Analysis in grazing incidence

• heat treatment up to @ 950°C, atm. pressure, air

The structure changes with temperature

BF-TEM image TiAlTaN

900 ºC (6 hrs)

200 nm

Crystalline oxide bilayer

Temperature induced phase changes in organic material

ANALYSIS OF PHASE TRANSFORMATIONS

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12 14 16 18 20 22 24 26 282Theta (°)

0

1

4

9

16

Inte

nsity (

cps)

12 14 16 18 20 22 24 26 282Theta (°)

0

1

4

9

16

Inte

nsity (

cps)

12 14 16 18 20 22 24 26 282Theta (°)

0

1

4

9

16

Inte

nsity (

cps)

25 °C 190 °C 140 °C

12 14 16 18 20 22 24 26 282Theta (°)

0

1

4

9

16

Inte

nsity (

cps)

130 °C

30 s 30 s 30 s

30 s

DoC = 48 % DoC = 0 %

DoC = 45 %

30 s

0

20

40

60

80

100

120

140

160

180

200

0 500 1000 1500 2000

TIME (S)

TE

MP

ER

AT

UR

E (

°C)

DoC = 0 %

Change in degree of crystallinity

(DoC) with temperature

Residual Stress Analysis

STRESS ANALYSIS

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Experimental set-up

• Parallel beam configuration

• χ-mode (Eulerian cradle)

(Reference: www.stanford.edu/group/glam/xlab/MatSci162_172/LectureNotes/05_Stress&Texture.pdf)

Ψ Ψ Ψ

Ψ>0 Ψ<0

Biaxial or uniaxial

stress Triaxial stress Texture

Intensity

150.0 152.4 154.8 157.2 159.6 (º2θ)

For different values of χ=Ψ

sin2 y method

Macrostrain / residual stress in

terp

lan

ar s

pac

ing

Investigation of Texture

TEXTURE ANALYSIS

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• Eulerian Cradle:

sample tilt: 0º< χ < 90º

sample rotation: 0º< ϕ < 360º

Example: Texture on rolled metal sample Investigation of industrial processes by texture:

Pole figures are symmetrical around ϕ=0º and ϕ=90º

Measured PF 200

Measured PF 111

Measured PF 220

Measured PF 311

RD

TD

Powders, dispersions Liquid crystals, Gels Fibres, Single crystals

Presence of texture

(picture by www.anton-paar.com)

Crystallite Size and Microstress

DETERMINATION OF CRYSTALLITE SIZE

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As size of crystallite decreases, width of

diffraction peak increases

Size

broadening

26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 2 q (deg.)

Inte

nsity (

a.u

.)

Microstress

broadening

Microstress can be introduced by: • surface tension of nanoparticles • morphology of crystal shape, such as nanotubes • interstitial impurities

In case where microstress is small, crystallite size can be determined

Layer thickness determination by XRR

X-RAY REFLECTOMETRY

16 VISICAT project (O. Ishchenko, D. Lenoble)

From fall in intensity and

period of interference fringes

• Thickness of thin films and multilayers

• Surface and interface roughness

From qc

• Material density

TiO2 layer thickness: 28 nm

model measured

Si substrate

TiO2 coating

(Measurement by I. Infante Canero and Y. Fleming)

Quantification of crystalline phases and amorphous content

QUANTITATIVE PHASE ANALYSIS

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Position [°2Theta] (Copper (Cu))

25 30 35 40 45

Counts

0

400

1600

3600

TiO2, Rutile 49.4 %

Fe2O3, Hematite 28.7 %

TiO2, Anatase 21.9 %

• Ways to estimate the amorphous phase content:

• By estimating the Degree of Crystallinity (DoC)

• By using a standard of known crystallinity (several methods)

Rutile, 49 wt%

Anatase, 22 wt%

Hematite, 29 wt%

(Scott A Speakman, Ph.D., http://prism.mit.edu/xray)

Small Angle X-ray Scattering vs. Wide Angle X-ray Scattering

TRANSMISSION IMAGING: SAXS/WAXS

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• SAXS provides: • Shape of particles

• Size of particles

• Particles’ surface per volume

• Particle characteristics:

• Liquid, solid or gaseous domains dispersed within a light

matrix

• 1 nm < size < 100 nm

• Concentration > 1 wt. %

• WAXS provides:

• Crystal nature

• Lattice parameters

• Crystal Amount

• Crystal Orientation

(picture by www.anton-paar.com)

Analysis of polystyrene/ZrO2 (95/5) nanocomposite

SAXS EXAMPLE

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1) Un-treated data 2) Corrections

3) Modelling

Spherical shape (model fitting)

Average diameter: 650 Å

Surface per volume: 0.136 Å-1

4) Analysis using the model curve

background subtraction absorption correction desmearing

Nanoclay structure alone

Polyamide + 5 wt.% nanoclay

18.3 Å 48.9 Å

Study of polymer / nanofiller interaction in the case of nanoclay

WAXS EXAMPLE

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Nanoclay intersheet distance from the (001) peak

The increase in clay intersheet distance indicates an intercalation mechanism

Structure changes due to load

ONGOING DEVELOPMENT

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Primary

optics

Miniature-tensile

device

Secondary

optics

• Coupling of tensile device and X-ray

scattering

• Identification of deformation mechanisms

of soft materials in terms of chain

orientation and damage

For more information, see Frederic Addiego’s presentation this afternoon

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Thank you for your attention!