1-SAMPLE
PREPARATION
The
preparation of samples for analysis by XRD is the responsibility of the user.
This is intended to reduce the probability of the analyzed specimen being
contaminated. This contamination can occur due to the sample holder not being
cleaned properly, other chemicals spilled during specimen preparation and
others. The height of the specimen exceeds or less than the height of the
sample holder as well as the inconsistency of the powder filled in the sample
holder can cause systematic errors in the XRD data. Thus, to ensure that the
data released by this laboratory meets the set standards, the preparation of
the sample is the responsibility of the user. XRD standard data using Silicon
(Si) will be supplied to users in need on request.
Proper sample
preparation is essential to getting highly quality XRD data. If you do not put
in the effort to properly prepare your sample, you can introduce errors that
make phase identification difficult to impossible and estimates of abundances
and crystallinity erroneous. Ideally, you need to achieve three conditions in
order to have good data:
- Total randomness of crystallite
orientations
- Sufficient number of crystallites to
get a representative intensity distribution for the sample
- Sufficient diffraction intensity to
meet satisfy counting statistics.
The best way to
make sure these conditions are met is to finely powder your sample.
2-SPECIMEN
ANALYSIS
Specimen
analysis using XRD depends on the objectives of the experiment conducted. The
parameters contained in the application form for the use of XRD need to be
adapted to the objectives of the study to obtain the required XRD data.
a.
Scan range
Generally,
scan range means minimum and maximum angle limits of 2θ when specimens are
analyzed using XRD. The setting depends on the position of at least 8 main
diffraction peaks based on the PDF card in the ICDD database. Users need to
check the PDF card first before setting the scan range. For example, if the
first diffraction peak is at 16.433o, then the minimum angle limit
of 2θ is 10.00o. If the eighth/ninth peak of diffraction is at an
angle of 67o, then the maximum limit setting is 70o.
Please
discuss and obtain approval from your supervisor first before setting the
appropriate scan range. Seek advice from the officer who approved the use of
XRD if necessary.
b.
Scan rate
Generally,
scan rate means the speed of X-ray scanning on the specimen. For experiments
for phase analysis, the recommended scan rate is 2o per minute. It
means an X-ray scan will take 2 minutes for every 2θ angle degrees. The scan
rate is suitable for the ratio of the diffraction peak to the background. If
the user has many samples that need to be analyzed, the scan rate can be
increased to up to 5o per minute provided the quality of the XRD
data should be compromised. It may be appropriate for the purpose of
preliminary validation of specimens by ensuring that certain diffraction peaks
exist in the XRD data to be obtained.
c.
Step size
Generally,
step size means an increase of 2θ angle degrees during XRD scanning. For
example, if the set step size is 0.02o, it means that the X-ray will
scan the specimen for every 0.02o angle of 2θ. Thus, the XRD data
will show that the 2θ readings are starting from 10.00o, 10.02o,
10.04o, 10.06o and until the maximum 2θ angle limit is reached.
Currently, the optimal step size is 0.02o and the user can refer to
any relevant reference to ensure the suitability of the step size with the
suitability of the XRD data to be obtained from the analyzed sample.
3-XRD
DATA ANALYSIS
The
XRD Laboratory is only responsible for ensuring that all users can analyze
their samples safely in accordance with the regulations, conditions and rules
of the XRD use under the Malaysian Atomic Energy Licensing Board. The
responsibility for analyzing the data obtained is the responsibility of the
user himself. Please ensure that the experimental parameters are appropriate to
the data requirements expected to be obtained through XRD. This ensures that
the data obtained from the experiments conducted can be used for scientific
research.
Appropriate
courses may be conducted to improve user understanding over time based on needs
and demands.
