IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
VI.12. X-ray Diffraction Studies using Imaging Plate as
an Area Detector
Imaging plate based X-ray
area detectors were initially
used for protein crystallography
in the 1980s and more recently,
their use has extended to smallmolecule
structural analyses
and powder diffractometry. The
usage of imaging plate is
particularly advantageous for
the characterization of
polycrystalline materials since it
permits simultaneous collection
of many orders of Bragg
reflections. There is also a
significant size advantage
compared to CCD based area
detector. In addition to the
enormous reduction of data
acquisition time for analyses,
two-dimensional diffraction
patterns contain much more
information than conventional
linear scans (i.e. - 2 scans)
collected using standard
powder diffractometers. Two
dimensional diffraction patterns
of polycrystalline samples
typically consist of concentric
(Debye-Scherrer) rings
produced by the superposition
of reflections from many
crystals illuminated by the X-ray
beam, which are oriented with
a set of (hkl) crystallographic
planes oriented to fulfill the
Bragg condition. Depending on
sample characteristics, these
rings might be continuous or
spotty and display specific
variation in the intensities along
them. These features contain
important information about
the microstructure of the
sample: grain size, preferential
orientation, mosaicity, stress
etc. Additionally, twodimensional
patterns can be
converted into conventional
linear scans by radial or
azimuthal integration of pixel
intensities. The generated linear
scans can be processed as
usual for mineral phase
identification, crystallinity or
Rietveld refinement studies.
Nevertheless, during this data
reduction procedure, most of
the information regarding the
microstructure of the material is
lost. Hence to get the full
advantage of two-dimensional
diffraction for polycrystalline
materials we have to extract the
information contained in the
two dimensional diffraction
patterns. Here we are reporting
the diffraction experiment
results obtained using the
imaging plate as an area
detector for both single crystal
and powder experiments. The
imaging plate reader has 5
mega pixel resolution for 250
mm X 200 mm size plate with
each pixel size of 100 the
data file size is 10 Mbytes.
Fig.1 Laue diffraction pattern of a Si single crystal obtained using the
Imaging plate as an area detector (the plate read using reader developed
at MSD IGCAR). The inset shows the maximum zoom of a diffraction point
and its intensity profile in surface and line plot.
Laue X-ray diffraction is
historically the first diffraction
method for structural
166 BASIC RESEARCH