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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, Germanylutz.bruegemann@bruker-axs.de+49 (0) 721 595 4307
Dr. Heiko RessMarketing ManagerBruker AXS Inc.Madison, Wisconsin, USAheiko.ress@bruker-axs.com+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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ICDD Intensity Round Robin MoO3Systematic Angular Errors
Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.
Systematic error + 0.06°
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ICDD Intensity Round Robin MoO3 Systematic Angular Errors
Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.
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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ICDD Intensity Round Robin MoO3Systematic Angular Errors
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
LYNXEYE with Fe-discrimination
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
LYNXEYE with Fe-discrimination
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
XRPD – Capillary Transmission
Aspirin in 1 mm capillaryBlack: focusing GMBlue: foc. Johansson
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XRPD – Capillary Transmission
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
XRPD – Capillary Transmission
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
XRPD – Capillary Transmission
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
XRPD - Capillary Transmission with Ag Radiation
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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XRPD - Capillary Transmission with Ag Radiation
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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Any Questions?
Please type any questions you may have in the Q&A panel and then
click Send.
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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