Transcript technical paper

Combined diffraction measurements for
independent determination of the 2q0error§
Suminar Pratapa & Brian O’Connor ¶
Materials Research Group, Department of Applied Physics
Curtin University of Technology, Perth, WA, Australia
§ Presented in the National Seminar and Workshop of X-ray Diffraction 2002,
17 September 2002 at Institute of Technology 10 November Surabaya (ITS), Indonesia
¶ Currently on leave from Department of Physics, Institute of Technology 10 November
Surabaya (ITS), Indonesia
What will be presented?
1. Importance of this study
2. How to do it?
3. Results  are they good?
4. What next?
IMPORTANCE OF THIS STUDY
Previous study using CeO2 NIST SRM
5 .4 1 4 00
NIST
c e rtifc a te
w ith S D
a n d q2-e ro r
r fin in g S D
e
2q-e ro r= 0
«1: 11, 000
SD= 0
re fin n
i g 2q-e ro r
5 .4 1 2 00
5 .4 1 1 00
5 .4 1 000
5 .4 09 00
5 .4 08 00
5 .4 07 00
Me th o d
SD = specimen displacement
«1: 2, 000
L a tic e c o n s
ta n t(in a n g s
tro m)
5 .4 1 3 00
«1: 500, 000
Lat t i ce const ant s det ermi ned usi ng Ri et vel d anal ysi s
IMPORTANCE OF THIS STUDY
2q0-error and specimen displacemnt error definition
D2q () = 2SD/Rcosq + 2q0
Both introduce systematic errors in lattice parameters.
IMPORTANCE OF THIS STUDY
Importance of Lattice Parameters
1. Theoretical density  porosity estimates
2. Thermal expansion coefficients
3. Linear strain
4. Chemical substitution
5. etc
Correction of 2q0- and specimen displacement errors
is absolutely essential!
IMPORTANCE OF THIS STUDY
QUESTION IS…..
What is the
2q0-error for the ITS
diffractometer¤?
¤ Philips
X’Pert
HOW TO DO IT?
Curtin Diffractometer
ITS Diffractometer
Combined measurements  diffraction data for MgO
ceramics were collected using both machines.
HOW TO DO IT?
From previous study…...
Current 2q0-error for Curtin
diffractometer is 0.0414.
HOW TO DO IT?
Reliability of the 2q0-error for Curtin diffractometer has
been verified using CeO2, Al2O3 and TiO2 NIST SRMs
with accuracy level between 1:50,000 and 1:120,000
following Rietveld refinement.
1. 2q0 was fixed at -0.041.
2. SD was refined. The sample holder used introduced
SD as much as 0.8 mm on average.
DETERMINATION OF 2q0-ERROR
FOR ITS DIFFRACTOMETER
Using 2q0 fixed at -0.041 of Curtin diffractometer the lattice constants of
the MgO ceramics were determined using Rietveld analysis. The lattice
constant for MgO ceramic 1450C-2h was used in the following:
0.05
The 2q0-error for
ITS diffractometer is
0.0209.
D2q
0.00
-0.05
D 2 q()-Mg Oc e ra mic
= 0 .0 2 0 9 - 0 .1 4 3 9qc o s
R2 = 0 .9 5 6 8
-0.1 0
0.00
0.1 0
0.2 0
0.3 0
0.4 0
c o sq
0.5 0
0.6 0
0.7 0
0.8 0
1 .00
4 .2 1 1 5
0.7 0
S p e c ime n d is
p la c e me n t( mm)
4 .2 1 1 6
4 .2 1 1 4
÷ 1 :5 0,000
4 .2 1 1 2
÷ 1 :4 0,000
4 .2 1 1 3
÷ 1 :1 00,000
L a tic e c o n s
ta n t(in a n g s
tro m)
Lattice parameter and specimen displacement for
MgO ceramics calculated by D2q vs. cosq
method (high-angle peaks only)
0.4 0
0.1 0
-0.2 0
C U R T IN
C U R T IN
IT S
4 .2 1 1 1
1 1 00-2 h
1 2 5 0-2 h
1 6 00-6 h
S p e c ime n
Accuracy of 1:50,000
is achievable.
IT S
-0.5 0
1 1 00-2 h
1 2 5 0-2 h
1 6 00-6 h
S p e c ime n
Similar SD for each XRD.
Conclusion
1. 2q0-error for ITS diffractometer has been determined with an
associated measurement using Curtin diffractometer. An MgO
ceramic has been used in this study.
2. Tests using MgO ceramics showed that the degree of accuracy is
approximately 1:50,000. Similar specimen displacement values
indicate the consistency in positioning the sample.
What next?
1. 2q0 correction should be applied to obtain high-accuracy lattice
constant values.
2. The method used in this study can be applied to obtain 2q0-error
for other diffractometers.
Acknowledgements
1. AusAID for providing PhD scholarship and
research travel support to ITS.
2. Curtin and ITS for providing support on this
collaborative work.