Good Diffraction Practice
Webinar Series
X-ray Reflectometry – Jul 21, 2010
Two-Dimensional XRD – Aug 11, 2010
h Powder XRD Instrumentation and
Data Quality – Sep 30, 2010
Welcome
2
Dr. Heiko Ress
Dr. Lutz Bruegemann
Marketing Manager
Bruker AXS Inc.
Madison, Wisconsin, USA
heiko.ress@bruker-axs.com
+1.608.276.3000
Director of Product Marketing & Development – XRD
Bruker AXS GmbH
Karlsruhe, Germany
lutz.bruegemann@bruker-axs.de
+49 (0) 721 595 4307
X-ray Powder Diffraction (XRPD)
Pattern = Intensity versus 2theta
3
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°
4
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°
„
„
„
„
„
5
Precision of peak position
Relative peak intensities
Peak shape
Full-Width-at-Half-Maximum (FWHM)
Peak-to-background ratio
ICDD Intensity Round Robin MoO3
Systematic Angular Errors
High quality
pattern
± 0.04°
Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.
6
ICDD Intensity Round Robin MoO3
Systematic Angular Errors
Systematic error + 0.06°
Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.
7
ICDD Intensity Round Robin MoO3
Systematic Angular Errors
Low Accuracy
High Precision
Jenkins & Schreiner (1989), Powder Diffraction 4, 74-100.
8
Accuracy and Precision
High Accuracy
High Precision
Low Accuracy
High Precision
9
High Accuracy
Low Precision
Low Accuracy
Low 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
Precision =repeatability= reproducibility
Key to Data Quality in XRPD
2-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 speed
„ Provides large torque for
loading components
10
Key to Data Quality in XRPD
D8 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
components
„ Maintenance free Gearing
11
Key to Data Quality in XRPD
2-Circle Goniometer
„ Larger diameter of
worm wheel Î
• more load capacity
• less wear out
• less sensitivity to load
changes
• Less sensitivity to
environmental changes
• Higher accuracy
Worm shaft
Worm wheel
Gearing of a simple milling machine
12
„ Remark: 1 micron
tooth height error
corresponds to
0.0004° angular error
Check the Accuracy and Precision
of a Goniometer
„ Heidenhain ROD
angular encoder
„ 36000 lines/360°
„ Measurement step:
0.000 005°
„ Accuracy: ±1” (0.0003)
Heidenhain ROD 880
13
„ Corresponds to ~30m
resolution of the earth’s
circumference at the
equator
D8 Goniometer – Accuracy and
Precision Validation
„ Accuracy <0.002° rms
„ Precision <0.0001° rms
„ NOTE: these values are
valid for the blank
goniometer
14
D8 Diffractometer – Fully Motorized
Setup for XRPD
X-ray
tube
Motorized
aperture
LYNXEYE
1-D detector
Tube
housing
alignment
base
Motorized
anti-scatter
slit
Sample
spinner
15
Accuracy and Precision of the
Measurement
Sample contributions
• Absorption (intrinsic!)
• Particle shape and size
• ...
Instrument contributions
• Geometry (intrinsic!)
• Alignment
• mechanics
• drive system
•….
Accuracy
and precision
of results
Sample preparation and
presentation
• Preferred orientation
• Beam overflow
• Displacement
• ...
16
Evaluation
• Modeling
• User errors
• Software error
• ...
Minimize the Sample Effects for XRPD
Ideal Powder sample:
„ Random arrangement of
crystallites
„ Amount of some 108 to
1010 crystallites
„ Crystallite sizes of the
order of some microns
Debye ring
X-Ray beam
sample
17
The XRPD Challenge – Real Samples
Powder
Micro
amount
Textured
material
Strained
material
XRD2 Pattern
Single
crystal
18
The XRPD Challenge
Diffraction rings from
powdered material
2Theta scan with
conventional
XRPD instrument
Spot from a single
crystallite
Spottiness effect
19
XRPD Accuracy and Precision
Magnitude of Errors
Jenkins & Snyder (1996), Introduction to X-ray powder Diffractometry.
AD: Axial divergence:
Max. deviation for low 2θ
angles
FS: flat specimen
Max. deviation for
medium 2θ range
DE: displacement error
Max. deviation for low 2θ
range
20
XRPD in Bragg-Brentano Geometry
Sample Transparency Error
Δ2Θ
„ 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
Sa mple
21
XRPD in Bragg-Brentano Geometry
Flat Specimen Error
Δ2Θ
Sa mple
22
„ Sample is tangent to the
variable focusing circle
leading to peak shifts and
asymmetric broadening
Î Small divergence slits help on
the expense of intensity
XRPD – Instrument Verification using
SRM 1976
23
2θ Accuracy Verification using
SRM 1976
Δ2θ
0.020
SRM 1976
Scinti
Vantec-1
LynxEye
0.015
0.010
0.005
0.000
-0.005
-0.010
-0.015
-0.020
20.00
24
40.00
60.00
80.00
2θ [°2θ]
100.00
120.00
140.00
Intensity Accuracy Verification using
SRM 1976
Ι/Ι1976
1.30
SRM 1976
Scinti
Vantec-1
LynxEye
1.20
1.10
1.00
0.90
0.80
0.70
20.00
25
40.00
60.00
80.00
2θ [°2θ]
100.00
120.00
140.00
Instrument Verification – Passed!
• Zero angle off-set: minimized
• Displacement error: minimized
• Receiving slit position error.
Minimized
• Axial Divergence Îproper
Soller
• Transparency, Flat Specimen
Î proper sample preparation
26
ICDD Intensity Round Robin MoO3
Systematic Angular Errors
Jenkins & Schreiner (1989),
Powder Diffr. 4, 74-100.
D8 ADVANCE: Δ2θ ≤ ±0.01°
27
XRPD and Background
„ 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
28
Peak-to-Background
XRPD on Fe-Containing Hematite
10000
Bragg-Brentano
geometry with 1-D
LYNXEYE detector
9000
8000
7000
counts
6000
5000
4000
3000
2000
1000
Fluorescence
background
0
20
40
60
2Theta [°]
29
8
Peak-to-Background
XRPD on Fe-Containing Hematite
11000
black: standard discriminator setting
10000
red: Fe optimized discriminator setting
9000
8000
LYNXEYE standard
discrimination
counts
7000
6000
5000
4000
3000
LYNXEYE with Fediscrimination
2000
1000
0
20
30
40
60
8
Peak-to-Background –
Scaled to Background Level
11000
LYNXEYE with Fediscrimination
10000
9000
8000
counts
7000
6000
LYNXEYE standard
discrimination
5000
4000
3000
2000
1000
0
32
34
2Theta [°]
31
36
Peak-to-Background –
Scaled to Background Level
11000
Peak-To-Background:
Improved from 4:1 to
15:1
10000
9000
8000
counts
7000
6000
5000
4000
3000
2000
1000
0
32
34
2Theta [°]
32
36
XRPD LYNXEYE versus Energy-Dispersive
SOL-XE – Fe2O3-containing Bauxite
LYNXEYE1-D standard
discrimination
3e4
2e4
1e4
6000
LYNXEYE with Fediscrimination
Log (Counts)
5000
4000
3000
2000
1000
Energy-dispersive
SOL-XE 0-D detector
300
250
10
20
30
40
2-Theta - Scale
Note: LYNXEYE still 30 times faster than energy-dispersive point detector
33
XRPD in Transmission Geometry
„ 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
34
The New D8 ADVANCE
Johansson monochromator
or Göbel mirror
LYNXEYE detector
Capillary sample holder
Anti-scatter slits /
beam stop
35
XRPD – Capillary Transmission
Aspirin in 1 mm capillary
Black: focusing GM
Blue: foc. Johansson
60000
3° 2theta
intensity [cps]
50000
40000
30000
20000
10000
0
3
10
20
30
40
50
2 T h e ta [ d eg ]
A s p i r in e c a p 1,0 - V a n t e c 1 0 - F il e : A s p i r in e F G M E S 2 5 s o l l N S 1,2 A S S c a p 1, 0 BS r a ds o l 2 ,5 s ol l V a n tec 1 0 - 5, 45 4 d e g m i n .r aw - T y pe : 2 T h a l o n e - S t a r t: 3 .00 0 0 ° - E n d : 6 0 .0 01 9 ° - St e p : 0 .0 07 3 ° - St e p ti m
O p e r a tio n s : Im p or t
A s p i r in e c a p 1,0 - L y nx E ye 3 - F i le : A s p ir i ne F G M E S 2 5 s ol l N S 1 ,2 A SS c a p 1 ,0 B S A S8 2 ,5 s o l l L X 3 - 5,8 8 2 de g m i n . r aw - T yp e : 2T h a lo ne - S t ar t: 3. 00 0 0 ° - E n d : 5 9 .9 9 9 9 ° - S t e p: 0 .0 0 6 9 ° - S t e p ti m e : 12 .4
O p e r a tio n s : Y S c a l e M u l 1 .0 79 | I m p o rt
0 0 - 01 2 - 0 85 0 (* ) - As p ir i n - 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 b y : 1 . - W L : 1 .5 40 6 - M on o c l in ic - a 11 .43 0 0 0 - b 6 .5 92 0 0 - c 11 .4 1 00 0 - a lp ha 9 0 .0 00 - b e t a 9 5. 65 0 - g a m m a 9 0 .0 00 - P r i m iti
36
60
XRPD – Capillary Transmission
31000
30000
Aspirin in 1 mm capillary
Black: focusing GM
Blue: foc. Johansson
29000
28000
27000
26000
25000
24000
23000
22000
21000
20000
intensity [cps]
19000
18000
17000
16000
15000
14000
13000
12000
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
20
21
22
23
24
25
2 Th e ta [ d eg ]
37
26
27
28
29
30
XRPD – Capillary Transmission
150
Pharmaceutical sample in 0.1 mm capillary
Blue: focusing Johansson
140
130
120
110
intensity [cps]
100
90
80
70
60
50
40
30
20
10
0
2
10
20
30
2Theta [deg]
File : 4 32 5 Vario ES2,0 5soller N S1 ,0 ASS BS AS8 2 ,5so ller LX3,5 - 0,7 s - 1 h.raw - St art: 2 .00 00 ° - St ep tim e: 12 5. 35 s - An od e: Cu
Op era tio ns: Im p ort
0 0-03 9-1 60 4 (I ) - D L-M ethion in e - C5 H11 NO2 S
38
40
50
XRPD – Capillary Transmission
1000
Pharmaceutical sample in 0.1 mm capillary
Blue: foc. Johansson
Black: foc. Goebel Mirror
900
800
700
intensity [cps]
600
500
400
300
200
100
0
2
10
20
30
2 Th e ta [ d eg ]
39
40
50
XRPD – Capillary Transmission
1000
Customer sample in capillary
Blue: foc. Johansson
Black: foc. Goebel Mirror
Better peak resolution
with Johansson
900
800
700
Better peak resolution
with Johansson
intensity [cps]
600
500
400
300
200
100
0
17
18
19
20
21
22
23
2 Th e ta [ d eg ]
40
24
25
26
27
28
XRPD with Shorter Wavelength
„ 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
41
XRPD with Shorter Wavelength –
Information Range
Normalized intensity (a.u.)
Normalized intensity (a.u.)
Sample LaB6
Same
angular
range
Fluorescence
1.9
1.8
1.7
d - Scale
λMo
λCu
4
3
2
1
0.9
0.8
0.7
d - Scale
42
0.6
0.5
0.4
XRPD with Shorter Wavelength –
Angular Resolution
0.090
LaB6 - reflection
0.080
LaB6 – capillary (0.1mm)
0.070
FWHM
0.060
0.050
0.040
0.030
0.020
8.0
13.0
18.0
23.0
28.0
33.0
°(2th)
43
38.0
43.0
48.0
53.0
58.0
XRPD - Capillary Transmission with
Ag Radiation
6000
Sample LaB6 prepared in 0.8 mm capillary
Focusing Göbel Mirror
LYNXEYE dedicated high-energy detector
5000
Intensity [counts]
100 min overall measurement time
4000
3000
2000
1000
0
10
20
30
40
50
60
70
80
2theta [deg]
44
90
100
110
120
130
140
XRPD - Capillary Transmission with
Ag Radiation
6000
Sample LaB6 prepared in 0.8 mm capillary
200
190
5000
180
170
160
Intensity [counts]
Intensity [counts]
150
4000
3000
140
130
120
110
100
90
80
70
60
50
40
30
2000
20
10
0
50
60
70
80
90
100
2theta [deg]
1000
0
10
20
30
40
50
60
70
80
2theta [deg]
45
90
100
110
120
130
140
XRPD - Capillary Transmission with
Ag Radiation
Rietveld Refinement
46
Conclusion
„
„
„
„
„
„
Accurate and precise peak position
Relative peak intensities
Resolution and full-width-at-half-maximum
Peak-to-background ratio
Transmission and reflection geometry
High-energy diffraction
„ ICDD PDF: a pattern is considered to be a high quality
pattern if Δ2θ≤ ±0.04°
Î Instrument should be capable to ensure Δ2θ ≤ ±0.02°
47
Any Questions?
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click Send.
48
To Learn More About Powder XRD
Bruker Training Central (BTC) – Online Training Courses
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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
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Basic Crystallography
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