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16.02.2010

Powder Neutron Diffraction - an introduction

Neutron scattering course – February 16, 2010

Magnus H. Sørby

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Scope

• The advantages of neutrons vs. X-rays

• Examples of neutron diffraction studies

• Neutron diffraction at IFE

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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.

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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AlloysWhich model is right for Mn0.6 Co0,4 ?

Neighboring elements

Random Co distribution

Ordered Co distributionX-rays:Z(Mn)=25Z(Co)=27

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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

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Alloys

Neighboring elements

Which model is right for Mn0.6 Co0.4 ?

Co selectively occupy the 8-fold position!

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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.

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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.

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Sample environment• Neutrons can penetrate several millimeters

of materials like aluminium and steel.

Furnace

Penetration depth

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Sample environment• Neutrons can penetrate several millimeters

of materials like aluminium and steel.

Cryostat

Penetration depth

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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.

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Study of large samples

Penetration depth

• How did the machining of the hole influence the material?

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Study of large samples

Penetration depth

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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)

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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.

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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.

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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

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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

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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

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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

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PUS – a high resolution diffractometer

Neutron diffraction at IFE

• In operation since 1997.

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PUS – a high resolution diffractometer

Neutron diffraction at IFE

• In operation since 1997.

Soller collimator (from Risø). 15’, 30’ and “open” (60’)

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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

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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)

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PUS – a high resolution diffractometer

Neutron diffraction at IFE

• In operation since 1997.

Oscillating radial collimators (MURR).

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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.

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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

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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

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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

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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

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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.