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

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