Dear Ficusia:
Extremely rare materials do not change their cell parameters when
temperature changes, some materials shrinking in particular temperature range
and most materials always expanding. Therefore fixing the cell parameters is
obviously not practical.
When temperature increases, thermal excitation becomes more and more
important and causes decreasing diffraction intensities and peak broadening. In
this case, Debye-Waller factors are neccessary to be handled.
In summary, cell parameters and DW factors can sufficiently explain
your temperature dependent diffraction patterns, i think. Except the two,
tuning experimental-condition parameters, including particle size, might be
auxiliary and sometimes tricky, but i don't think exp. parameters can
substantially account your results.
Faithfully
Jun Lu
----------
Lst. Prof. Lijie Qiao
Department of Materials Physics and Chemistry
University of Science and Technology Beijing
100083 Beijing
P.R. China
http://www.instrument.com.cn/ilog/handsomeland/
Lst. Prof. Loidl and Lunkenheimer
Experimental Physics V
Center for Electronic Correlations and Magnetism (EKM)
University of Augsburg
Universitaetsstr. 2
86159 Augsburg
Germany
http://www.physik.uni-augsburg.de/exp5
----- Original Message -----
From: ficu...@yahoo.com
To: rietveld_l@ill.fr
Sent: Friday, July 24, 2009 8:10 AM
Subject: XRD data: particle size, cell size etc
I use to do XRD from room temperature to High temperature and then
cooling again at room temperature.
I see there is constant going to the right for all the peaks and also
their intensities are decreasing, also the width of peaks is becoming larger.
I would like to interpret those data and also to calculate the particle
size and the unit cell size (if there is a change with the temperature).
It seems the phase is not change only the shits and the intensities
values.
I would like to calculate taking in account the data I have (Intensity
vs. 2*theta plot)
I found a formula but there is included the unit cells parameters and I
do not want to use that, because my goal is to find the unit cell parameter
using the recorded data for each set of data.
* How to interpret the constant moving of my intensities to the right
with each temperature step?
*How to interpret the constant decreasing in intensity of every peak
with each temperature step?
*How to interpret the constant increasing wide each peak with each
temperature step?
Could you help me to interpret those data or to guide to read something
on the web to help me with this?
Thank you!
