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16.02.2010
Powder Neutron Diffraction - an introduction
Neutron scattering course – February 16, 2010
Magnus H. Sørby
16.02.2010
Scope
• The advantages of neutrons vs. X-rays
• Examples of neutron diffraction studies
• Neutron diffraction at IFE
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.Can distinguish neighboring elements in the
periodic table.
• The neutron interacts weakly with matter.Complicated sample environment is possible.Large samples can be studied.Scattering from bulk; not just the surface.
• The neutron has a magnetic moment.Can study magnetic ordering.
16.02.2010
Metal hydrides• Materials that contain chemical bonding
between metal- and hydrogen atoms.
Light and heavy elements
4 kg H2
L. Schlapbach, A. Zuttel Nature 414 (2001) 353-358
300 kg
Mg2 NiH4 LaNi5 H6 Liquid H2 H2 gas (200 bar)
M(s) + x/2 H2(g) MHx(s) + energy
16.02.2010
Alanates AlH
AlH4-
Al
H
AlH63-
3 NaAlH4 Na3 AlH6 + 2 Al + 3 H2 3.7wt% ~120C
Na3 AlH6 3 NaH + Al + 3/2 H2 1.9wt% ~180C
NaH Na + ½ H2 1.9wt% 425C
B. Bogdanovic, J. Alloys Comp. 253-254 (1997) 1-9.
5.6 wt%
TiCl3
TiCl3
Light and heavy elements
16.02.2010
Li3 AlD6 seen by neutrons
ac
Li3 AlD6 seen by X-rays
PUS - high resolution diffractometer
The JEEPII reactor
Crystal structure of alanates
Al
D
Light and heavy elements
NaAlH4Na3 AlH6LiAlH4-LiAlH4Li3 AlH6KAlH4Mg(AlH4 )2Sr2 AlH7BaAlH5Ba2 AlH7Na2 LiAlH6K2 NaAlH6LiMg(AlH4 )2LiMgAlH6Ca(AlD4 )2CaAlD5
16.02.2010
NaAlD4
Na2 LiAlH6
LiAlD4
KAlD4
LiMgAlD6
K2 NaAlD6
-LiAlD4
LiMg(AlD4 )3
Li3 AlD6
Mg(AlH4 )2
Crystal structure of alanates
Diversity• Symmetries ranging from cubic to monoclinic• A variety of local configuration.
ab
c a
bc
ab
c
LiAlD4CN(Li-D) = 5P21 /c [1]
NaAlD4CN(Na-D) = 8I41 /a [2]
KAlD4CN(K-D) = 10Pnma [3]
[1] B. C. Hauback, et al., J. Alloys Comp. 346 (2002) 184-189.[2] B. C. Hauback, et al., J. Alloys Comp. 358 (2003) 142-145.[3] B. C. Hauback, et al., J. Alloys Comp. 394 (2005) 35-38.
Light and heavy elements
16.02.2010
NaAlD4
Na2 LiAlH6
LiAlD4
KAlD4
LiMgAlD6
K2 NaAlD6
-LiAlD4
LiMg(AlD4 )3
Li3 AlD6
Mg(AlH4 )2
Crystal structure of alanates
Diversity• Symmetries ranging from cubic to monoclinic• A variety of local configuration
Similarities• Average Al-D: 1.60-1.64 Å (AlD4
-) 1.74-1.80 Å (AlD6
3-)
Na2 LiAlD6
Al-D = 1.760(1) Å, a = 7.385 Å [1]
K2 NaAlH6
Al-H = 1.759(1) Å, a = 8.118 Å [2]
[1] H. W. Brinks, et al., J. Alloys Comp. 392 (2005) 27-30.[2] M. H. Sørby, et al., J. Alloys Comp. 415 (2006) 284-287.
Fm3m
Light and heavy elements
16.02.2010
a
b
c
NaAlD4
Na2 LiAlH6
LiAlD4
KAlD4
LiMgAlD6
K2 NaAlD6
-LiAlD4
LiMg(AlD4 )3
Li3 AlD6
Mg(AlH4 )2
Crystal structure of alanates
R3 a = 8.071 Å c = 9.513 Å
Li3 AlD6pseudo-bcc packing of AlD6
3-
Li+ in ½ of tetrahedral sites
Diversity• Symmetries ranging from cubic to monoclinic• A variety of local configuration
Similarities• Average Al-D: 1.60-1.64 Å (AlD4
-) 1.74-1.80 Å (AlD6
3-)• Anion sublattice often related to simple
sphere packing structures.
Light and heavy elements
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.• Can distinguish neighboring elements in the
periodic table.• The neutron interacts weakly with matter.
Complicated sample environment is possible.Large samples can be studied.Scattering from bulk; not just the surface.
• The neutron has a magnetic moment.Can study magnetic ordering.
16.02.2010
Alloys-Mn: Cubic, complex structure, a = 6.31 Å,
Z = 20
Neighboring elements
Mn(1)12 Mn(2)8What happens if 40% of the Mn is substituted with Co?
a
16.02.2010
Alloys-Mn: Cubic, complex structure, a = 6.31 Å,
Z = 20
Neighboring elements
[Mn0.6 Co0.4 ](1)12 [Mn0.6 Co0.4 ](2)8What happens if 40% of the Mn is substituted with Co?
a
16.02.2010
Alloys-Mn: Cubic, complex structure, a = 6.31 Å,
Z = 20
Neighboring elements
What happens if 40% of the Mn is substituted with Co?
Mn(1)12 Co(2)8a
16.02.2010
AlloysWhich model is right for Mn0.6 Co0,4 ?
Neighboring elements
Random Co distribution
Ordered Co distributionX-rays:Z(Mn)=25Z(Co)=27
16.02.2010
Alloys
Neighboring elements
Random Co distribution
Ordered Co distributionX-rays:Z(Mn)=25Z(Co)=27
Neutrons:b(Mn)=-0.373b(Co)=+0.249
Which model is right for Mn0.6 Co0.4 ?
Random Co distribution
Ordered Co distribution
16.02.2010
Alloys
Neighboring elements
Which model is right for Mn0.6 Co0.4 ?
Co selectively occupy the 8-fold position!
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.• Can distinguish neighboring elements in the
periodic table.
• The neutron interacts weakly with matter.• Complicated sample environment is possible.Large samples can be studied.Scattering from bulk; not just the surface.
• The neutron has a magnetic moment.Can study magnetic ordering.
16.02.2010
Sample environment
Penetration depth
• Neutrons can penetrate several millimeters of materials like aluminium and steel.
Sample container (Inconel super-alloy) rated to 3000 bar and 600oC.
16.02.2010
Sample environment• Neutrons can penetrate several millimeters
of materials like aluminium and steel.
Furnace
Penetration depth
16.02.2010
Sample environment• Neutrons can penetrate several millimeters
of materials like aluminium and steel.
Cryostat
Penetration depth
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.• Can distinguish neighboring elements in the
periodic table.
• The neutron interacts weakly with matter.• Complicated sample environment is possible.• Large samples can be studied.Scattering from bulk; not just the surface.
• The neutron has a magnetic moment.Can study magnetic ordering.
16.02.2010
Study of large samples
Penetration depth
• How did the machining of the hole influence the material?
16.02.2010
Study of large samples
Penetration depth
16.02.2010
Study of large samples
Penetration depth
3D residual stress-field can be mapped in a non-destructive way!
Loading a sample at the NRSF2 instrument at Oak Ridge National Lab (US)
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.• Can distinguish neighboring elements in the
periodic table.• The neutron interacts weakly with matter.
• Complicated sample environment is possible.• Large samples can be studied.• Easy interpreations of scattering intensities
are easily.• The neutron has a magnetic moment.
Can study magnetic ordering.
16.02.2010
Scattering intensity2
)( 22
)( 22 i
lzkyhxii
i
KriiK
iiii ebebFI
• Can (usually) neglect effects of multiple scattering, extinction and absorption.
16.02.2010
The glory of neutrons• There is no systematic correlation between
atomic number and the scattering length.• Can get information about light and heavy
elements simultaneously.• Can distinguish neighboring elements in the
periodic table.• The neutron interacts weakly with matter.
• Complicated sample environment is possible.• Large samples can be studied.• Easy interpreations of scattering intensities are
easily.• The neutron has a magnetic moment.
• Can study magnetic ordering.
16.02.2010
Magnetic neutron scattering• The neutron has a
magnetic moment.• This will interact with the
magnetic moment of atoms with unpaired electrons.
Magnetic scattering
unit scattering vector, K magnetic spin
direction, Mincident beam
diffracted beam
i
lzkyhxiiihklmagnetic
iiiefmF )( 2,
MKm
MKm
mMMKKm
,1
,0
sin,)(
|| 2
,2
,2
hklmagnetichklnuclhklhkl FFFI
16.02.2010
Magnetic neutron scattering
Magnetic scattering
5 10 15 20 25 30 35
0
50
100
150
200
250
300
350
400
450
Inte
nsity
(arb
. uni
ts)
2 (deg.)
100
111
110Nuclear scattering
16.02.2010
Magnetic neutron scattering
Magnetic scattering
5 10 15 20 25 30 35
0
50
100
150
200
250
300
350
400
450
Inte
nsity
(arb
. uni
ts)
2 (deg.)Ferromagnetic
100
111
110Nuclear scatteringMagn. scatteringTotal scattering
16.02.2010
Magnetic neutron scattering
Magnetic scattering
5 10 15 20 25 30 35
0
50
100
150
200
250
300
350
400
450
Inte
nsity
(arb
. uni
ts)
2 (deg.)Antiferromagnetic
Nuclear scatteringMagn. scatteringTotal scattering
100
111
110
½00 ½10 ½11
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
Soller collimator (from Risø). 15’, 30’ and “open” (60’)
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
Vertically focusing Cu monochromator (from Risø).311, 511 or 711 reflection plane can be used
= 0.75-2.60 Å
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
Sample temperature: 8 – 1200KGas pressures up to 8 bar (soon 100 bar)
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
Oscillating radial collimators (MURR).
16.02.2010
PUS – a high resolution diffractometer
Neutron diffraction at IFE
• In operation since 1997.
2 detector banks with 7 vertically stacked position sensitive detectors in each. Each bank cover 20o scattering angle.
16.02.2010
R2D2- a second-hand powder diffractometer
SANS
Staircase
Cold Moderator
JEEP II
To Air
Lock 12
3
4
5
6
7
89
10
10 m
R2D2
TOF
PUS 1
DIFF
Reflectometer
Nye instrumenter
16.02.2010
R2D2
• moved from Risø (TAS3) to Studsvik in 2000.
• moved from Studsvik to Kjeller in 2005.
• resolution as PUS.• ... but only 1/6 of the intensity.• operational in a few months
New instruments
- a second-hand powder diffractometer
16.02.2010
ODIN- a brand new powder diffractometer
SANS
ODIN
Staircase
Cold Moderator
JEEP II
To Air
Lock 12
3
4
5
6
7
89
10
10 m
R2D2
PUS 1
DIFF
Reflectometer
New instruments
16.02.2010
ODIN
• Optimized DIffractometer for Neutrons
• All aspects of the design is optimized by Monte Carlo simulations.
• 3.5 times higher intensity at slightly better resolution than PUS.
• Or 15 times higher intensity at lower resolution.
New instruments
- a brand new powder diffractometer
16.02.2010
Conclusion• Powder Neutron Diffraction give unique
structural information about:• Compounds that contain both light and heavy
elements.• Compounds that contain elements of similar weight.• Samples under high pressure and extreme
temperatures.• Large samples like machine parts.• Magnetic materials.