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This lecture was given at the IUCr (International Union of Crystallography) meeting in Madrid, 2011. Contents are focussed on the use of precession electron diffraction for functional materials, mainly lithium based battery materials, but also a perovskite was included, since a large part of the audience worked on that subject.
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Joke Hadermann
Artem M. Abakumov
Tyché Perkisas
Zainab Hafideddine
Stuart Turner
Gustaaf Van Tendeloo
Nellie R. Khasanova
Evgeny V. Antipov
University of Antwerp, Belgium
Moscow State University, Russia
Transmission electron microscopy
...
Transmission electron microscopy
Electron Diffraction
Precession
Electron Diffraction
Transmission electron microscopy
Precession
Electron Diffraction
Precession electron diffraction
DOES
allow structure solution and refinement
from ED data
Precession electron diffraction
Vincent, R. & Midgley, P. A. Ultramicroscopy 53 (1994) , 271-282.
The problem:
Structure cannot be solved from powder diffraction
There are no single crystals.
The solution:
Achieve single crystal diffraction of the powder
sample through precession electron diffraction.
Example: Li2CoPO4F
First, electron diffraction
patterns are taken, using the
precession attachment.
All patterns can be indexed using the cell
parameters and space groups known from XRD:
a= 10.452(2) Å, b= 6.3911(8) Å, c=10.874(2) Å
Pnma
The intensities of the observed peaks are extracted
Geometric corrections applied
We now have intensities of
237 symmetry unique reflections
Merged into one list
Intensities of 237
symmetry unique
reflections
Li2CoPO4F
a= 10.452(2) Å,
b= 6.3911(8) Å,
c=10.874(2) Å
Pnma
&
INTO
Direct Methods
Result: R=31%
Co and P ≈ Li2FePO4F
but
Li, O, F mixed up
F: tetrahedra around P
O: complete octahedra around Co
Remaining positions (purple): Li or ghosts?
Difference Fourier maps
Straight from direct methods:
too many Li(?) peaks
Difference Fourier allows
to eliminate the grey ones
Structure is solved !
Can be refined...
Separate list of intensities per zone into
Jana2006 using separate scale factors
Use PO4 rigid units:
18 variables reduced to 6
R=24% (reasonable for precession
electron diffraction data)
&
Solved Refined
PED can be successfully applied
for the crystallographic characterization
of Li-based battery materials
Li2CoPO4F was successfully solved and
refined from precession electron diffraction
A perovskite based example:
Pb13Mn9O25
Starting point:
a powder sample with nominal
composition Pb2Mn2O5
Electron diffraction reveals three phases...
Pnma; a= 5.7 Å, b=3.8 Å, c= 22 Å
P4/m; a=b=14.2Å=ap√13c=3.9 Å=ap
1
2
3 In progress
ED, HAADF-STEM, EDX
Pb
Mn
Pb2Mn2O5
1
cf.
MS79 P02
MS88 P12
No solution from conventional (S)TEM2
Precession electron diffraction
Tilt series around a* axis: [100], [102], [103], [104], [105] + [001]
100 unique reflections in P4/m2/12 ))R2/g(1(g)R,g(C
Problems expected for direct methods!
Have to find positions for
oxygen (Z=8) while main
impact from Pb(Z=82)
PED-data,
composition PbMnO2.5,
cell pars+SG
R=34%
There are ordered
manganese vacancies.
There are ordered
manganese vacancies.
But where is
the oxygen?
Global optimization in direct space
(FOX)
Structure optimisation
E = -7.42 eVE = -11.1 eV
Structure of Li2CoPO4F
solved using PED.
Structure of Pb13Mn9O25
solved using PED.
Presence of cubic phase
in layered phase LiCoO2
nanoparticles sample
detected by PED.
For a more detailed treatment:
“Solving the Structure of Li Ion Battery Materials with Precession
Electron Diffraction: Application to Li2CoPO4F”
Chem. Mater., 2011, 23 (15), pp 3540–3545http://pubs.acs.org/doi/abs/10.1021/cm201257b
“Direct space structure solution from precession electron diffraction data:
Resolving heavy and light scatterers in Pb13Mn9O25 ”
Ultramicroscopy, 2010, 110, pp 881-890Ultramicroscopy 110 (2010) 881–890
“New perovskite based manganite Pb2Mn2O5”
Journal of Solid State Chemistry, 2010, 183 (9), pp 2190-2195Journal of Solid State Chemistry, Volume 183, Issue 9, p. 2190-2195
www.slideshare.net/johader