good diffraction practice webinar series · x-ray powder diffraction (xrpd) pattern = intensity...

$: Good Diffraction Practice Webinar Series · X-ray Powder Diffraction (XRPD) Pattern = Intensity versus 2theta 3. XRPD – Definition of Quality ICDD PDF: a pattern is considered to$
Good Diffraction Practice

Webinar Series

X-ray Reflectometry – Jul 21, 2010

Two-Dimensional XRD – Aug 11, 2010

Powder XRD Instrumentation and

Data Quality – Sep 30, 2010

Welcome

Dr. Lutz BruegemannDirector of Product Marketing & Development – XRDBruker AXS GmbHKarlsruhe, [email protected]+49 (0) 721 595 4307

Dr. Heiko RessMarketing ManagerBruker AXS Inc.Madison, Wisconsin, [email protected]+1.608.276.3000

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X-ray Powder Diffraction (XRPD)Pattern = Intensity versus 2theta

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XRPD – Definition of Quality

ICDD PDF: a pattern is considered to be a high quality pattern if differences between measured and theoretical peak positions:

Δ2θ≤ ±0.04°

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XRPD – Definition of Data Quality

ICDD PDF: a pattern is considered to be a high quality pattern if the difference between measured and predicted peak position:

Δ2θ ≤ ±0.04°

Precision of peak positionRelative peak intensitiesPeak shapeFull-Width-at-Half-Maximum (FWHM)Peak-to-background ratio

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ICDD Intensity Round Robin MoO3Systematic Angular Errors

Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.

± 0.04°

High quality pattern

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Systematic error + 0.06°

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ICDD Intensity Round Robin MoO3 Systematic Angular Errors


Low AccuracyHigh Precision

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Accuracy and Precision

Accuracy is the degree of closeness of measurements of a quantity to its actual (true) value

Precision is the degree to which repeated measurements under unchanged conditions show the same results

High AccuracyHigh Precision

Low AccuracyLow Precision

Low AccuracyHigh Precision

High AccuracyLow Precision

Precision =repeatability= reproducibility9

Key to Data Quality in XRPD2-Circle Goniometer

A goniometer is an instrument that either measures angle or allows an object to be rotated to a precise angular position

High positioning speedProvides large torque for loading components

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Key to Data Quality in XRPDD8 2-Circle Goniometer

Stepper motors and optical encoder:• Minimum step size

0.0001°• Precision ±0.0001°• Accuracy: ± 0.005°

Dovetail tracks for mounting primary and diffracted beam componentsMaintenance free Gearing

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Key to Data Quality in XRPD2-Circle Goniometer

Larger diameter of worm wheel • more load capacity• less wear out• less sensitivity to load

changes• Less sensitivity to

environmental changes• Higher accuracy

Remark: 1 micron tooth height error corresponds to 0.0004° angular error

Worm shaft Worm wheelGearing of a simple milling machine

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Check the Accuracy and Precision of a Goniometer

Heidenhain ROD angular encoder36000 lines/360°Measurement step: 0.000 005°Accuracy: ±1” (0.0003)

Corresponds to ~30m resolution of the earth’s circumference at the equator

Heidenhain ROD 880

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D8 Goniometer – Accuracy and Precision Validation

Accuracy <0.002° rms

Precision <0.0001° rms

NOTE: these values are valid for the blank goniometer

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D8 Diffractometer – Fully Motorized Setup for XRPD

Motorized aperture

Sample spinner

LYNXEYE1-D detectorTube

housing alignment

base

X-ray tube

Motorized anti-scatter

slit

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Accuracy and Precision of the Measurement

Sample contributions• Absorption (intrinsic!)• Particle shape and size• ...

Evaluation• Modeling• User errors• Software error• ...

Sample preparation andpresentation• Preferred orientation• Beam overflow• Displacement• ...

Instrument contributions• Geometry (intrinsic!)• Alignment • mechanics• drive system•….

Accuracy and precision

of results

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Minimize the Sample Effects for XRPD

Ideal Powder sample:Random arrangement of crystallitesAmount of some 108 to 1010 crystallitesCrystallite sizes of the order of some microns

Debye ring

sample

X-Ray beam

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Single crystal

Microamount

Textured material

Powder

Strainedmaterial

The XRPD Challenge – Real Samples

XRD2 Pattern

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The XRPD Challenge

Spot from a single crystallite

2Theta scan with conventional

XRPD instrument

Diffraction rings from powdered material

Spottiness effect

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XRPD Accuracy and PrecisionMagnitude of Errors

Jenkins & Snyder (1996), Introduction to X-ray powder Diffractometry.

FS: flat specimenMax. deviation for medium 2θ range

DE: displacement errorMax. deviation for low 2θ

range

AD: Axial divergence:Max. deviation for low 2θ angles

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XRPD in Bragg-Brentano Geometry Sample Transparency Error

For weakly absorbing samples the average diffracting surface lies below the physical sample surface leading to peak shifts and asymmetric broadening

Note:The sample transparency error is equivalent to the sample displacement error

Sample

Δ2Θ

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XRPD in Bragg-Brentano Geometry Flat Specimen Error

Sample is tangent to the variable focusing circle leading to peak shifts and asymmetric broadeningSmall divergence slits help on the expense of intensity

Sample

Δ2Θ

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XRPD – Instrument Verification using SRM 1976

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2θ Accuracy Verification using SRM 1976

SRM 1976

20.00 40.00 60.00 80.00 100.00 120.00 140.002θ [°2θ]

-0.020

-0.015

-0.010

-0.005

0.000

0.005

0.010

0.015

0.020Δ2θ

ScintiVantec-1LynxEye

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Intensity Accuracy Verification using SRM 1976

SRM 1976

20.00 40.00 60.00 80.00 100.00 120.00 140.002θ [°2θ]

0.70

0.80

0.90

1.00

1.10

1.20

1.30

Ι/Ι1976

ScintiVantec-1LynxEye

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Instrument Verification – Passed!

• Zero angle off-set: minimized• Displacement error: minimized• Receiving slit position error.

Minimized

• Axial Divergence proper Soller

• Transparency, Flat Specimen proper sample preparation

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Jenkins & Schreiner (1989), Powder Diffr. 4, 74-100.

D8 ADVANCE: Δ2θ ≤ ±0.01°

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Reasons for background in a pattern• Diffraction of non-characteristic emissions of the X-ray tube• Air scattering• Sample fluorescence• In-proper beam path shielding, in particular when measuring

at very low angles• Over-illumination of the sample

Detector and electronic noise is not relevant if below 0.5 cps

XRPD and Background

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coun

ts

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

2Theta [°]20 40 60 8

Peak-to-BackgroundXRPD on Fe-Containing Hematite

Fluorescence background

Bragg-Brentano geometry with 1-D LYNXEYE detector

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coun

ts

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

20 40 60 8

black: standard discriminator setting

red: Fe optimized discriminator setting

Peak-to-BackgroundXRPD on Fe-Containing Hematite

LYNXEYE standarddiscrimination

LYNXEYE with Fe-discrimination

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Peak-to-Background –Scaled to Background Level

coun

ts

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

2Theta [°]32 34 36

LYNXEYE standarddiscrimination


Peak-to-Background –Scaled to Background Level

coun

ts

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

2Theta [°]32 34 36

Peak-To-Background:Improved from 4:1 to

15:1

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XRPD LYNXEYE versus Energy-Dispersive SOL-XE – Fe2O3-containing Bauxite

Log

(Cou

nts)

250

300

1000

1e4

2000

3000

4000

5000

6000

2e4

3e4

2-Theta - Scale

10 20 30 40

Note: LYNXEYE still 30 times faster than energy-dispersive point detector

LYNXEYE1-D standarddiscrimination


Energy-dispersiveSOL-XE 0-D detector

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Low absorbing samples → Transmission geometry avoids transparency error as present in Bragg-Brentano reflection geometry

Very small sample amount → Transmission geometry minimizes illuminated sample area errors

Environmental sensitive samples → Transmission geometry with fused capillaries keep the sample stable for the required measurement time

Transmission geometry with capillary technique in common provides the smallest full-width-at-half-maximum peaks

XRPD in Transmission Geometry

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The New D8 ADVANCE

Johansson monochromatoror Göbel mirror

Capillary sample holder

LYNXEYE detector

Anti-scatter slits /beam stop

XRPD – Capillary Transmission

0 0-01 2-0 85 0 (* ) - As p ir in - C 9 H 8 O 4/C H 3 C O 2· C 6 H 4· C O 2 H - Y: 5 0.0 0 % - d x by : 1 . - W L : 1 .5 40 6 - M on oc l in ic - a 11 .43 00 0 - b 6.5 92 00 - c 11 .4 100 0 - a lp ha 90 .0 00 - b et a 9 5. 65 0 - ga m m a 9 0.0 00 - P r im itiO p era tio ns : Y S c ale M ul 1 .0 79 | I m po rtA s pir in e c ap 1,0 - L y nx E ye 3 - F i le : A s p ir ine F G M E S 2 5s ol l N S 1 ,2 A SS c a p1 ,0 B S A S8 2 ,5 s ol l LX 3 - 5,8 82 de gm in. raw - T yp e: 2T h a lo ne - S t ar t: 3. 00 00 ° - E nd : 59 .99 99 ° - S t ep: 0 .00 69 ° - S t ep tim e: 12 .4O p era tio ns : Im p or tA s pir in e c ap 1,0 - V a nt ec 10 - F ile : A s pir in e F G M ES 2 5 s ol l N S 1,2 A S S c ap 1, 0 BS ra ds o l 2,5 s ol l V an tec 1 0 - 5, 45 4d eg m in .raw - T y pe : 2 T h a lon e - St ar t: 3 .00 00 ° - E n d: 60 .0 01 9 ° - St ep : 0 .0 07 3 ° - St ep tim

inte

nsity

[cps

]

0

1 0 0 0 0

2 0 0 0 0

3 0 0 0 0

4 0 0 0 0

5 0 0 0 0

6 0 0 0 0

2 Th e ta [d eg ]3 1 0 2 0 3 0 4 0 5 0 6 0

Aspirin in 1 mm capillaryBlack: focusing GMBlue: foc. Johansson3° 2theta

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inte

nsity

[cps

]

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1000 0

1100 0

1200 0

1300 0

1400 0

1500 0

1600 0

1700 0

1800 0

1900 0

2000 0

2100 0

2200 0

2300 0

2400 0

2500 0

2600 0

2700 0

2800 0

2900 0

3000 0

3100 0

2Th e ta [deg ]20 21 2 2 23 24 25 26 27 28 29 30


Aspirin in 1 mm capillaryBlack: focusing GMBlue: foc. Johansson

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00-039-1604 (I ) - DL-Methion ine - C5H11NO2SOperations: ImportFile : 4325 Vario ES2,0 5soller NS1,0 ASS BS AS8 2,5so ller LX3,5 - 0,7s - 1h.raw - Start: 2.0000 ° - Step time: 125.35 s - Anode: Cu

inte

nsity

[cps

]

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

2Theta [deg]2 10 20 3 0 40 50

Pharmaceutical sample in 0.1 mm capillaryBlue: focusing Johansson

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inte

nsity

[cps

]

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

7 0 0

8 0 0

9 0 0

1 0 0 0

2 Th e ta [d eg ]2 1 0 2 0 3 0 4 0 5 0


Pharmaceutical sample in 0.1 mm capillaryBlue: foc. JohanssonBlack: foc. Goebel Mirror

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inte

nsity

[cps

]

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

7 0 0

8 0 0

9 0 0

1 0 00

2 The ta [deg ]17 18 19 20 21 22 2 3 2 4 2 5 2 6 2 7 2 8


Customer sample in capillaryBlue: foc. JohanssonBlack: foc. Goebel Mirror

Better peak resolution with Johansson

Better peak resolution with Johansson

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Shorter wavelength → larger d-range, more information… but, also more peak overlap

High energy radiation reduces sample absorption… but, also detector efficiency

Avoids fluorescence for some elements… but, may excite it for other elements

XRPD with Shorter Wavelength

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Nor

mal

ized

inte

nsity

(a.u

.)

d - Scale0.41 0.50.60.70.80.9234

XRPD with Shorter Wavelength –Information Range

λMo

λCu

Same angular range

Nor

mal

ized

inte

nsity

(a.u

.)

d - Scale1.71.81.9

Fluorescence

Sample LaB6

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XRPD with Shorter Wavelength –Angular Resolution

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

8.0 13.0 18.0 23.0 28.0 33.0 38.0 43.0 48.0 53.0 58.0

°(2th)

FWH

M

LaB6 - reflection

LaB6 – capillary (0.1mm)

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Inte

nsity

[cou

nts]

0

1000

2000

3000

4000

5000

6000

2theta [deg]10 20 30 40 50 60 70 80 90 100 110 120 130 140

XRPD - Capillary Transmission with Ag Radiation

Sample LaB6 prepared in 0.8 mm capillaryFocusing Göbel MirrorLYNXEYE dedicated high-energy detector100 min overall measurement time

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Inte

nsity

[cou

nts]

0

1000

2000

3000

4000

5000

6000

2theta [deg]10 20 30 40 50 60 70 80 90 100 110 120 130 140


Sample LaB6 prepared in 0.8 mm capillary

Inte

nsity

[cou

nts]

010

2030

4050

607080

90100

110120

130140

150160170

180190

200

2theta [deg]50 60 70 80 90 100

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Rietveld Refinement

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Conclusion

Accurate and precise peak positionRelative peak intensitiesResolution and full-width-at-half-maximumPeak-to-background ratioTransmission and reflection geometryHigh-energy diffraction

ICDD PDF: a pattern is considered to be a high quality pattern if Δ2θ≤ ±0.04°Instrument should be capable to ensure Δ2θ ≤ ±0.02°

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To Learn More About Powder XRD

Bruker Training Central (BTC) – Online Training CoursesWeb-based training courses delivered through your browserInclude slides, audio, video and participant Q&AUpcoming live:• Oct 5-6 – X-ray Reflectometry (2 hrs)

On-demand:• Fundamentals of Powder XRD• Powder XRD Data Acquisition & Analysis• Basics of Two-Dimensional XRD• Getting Started with LEPTOS• Getting Started with TOPAS• Basic Crystallography

Free on-demand webinars: www.bruker-axs.com/webinars_xrd.htmlUpcoming live webinars: www.bruker-webinars.com

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good diffraction practice webinar series · x-ray powder diffraction (xrpd) pattern = intensity...

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