magnetic materials in sustainable energy · rare earth metals, recycling magnetocaloric materials...

O. GutfleischMagnetic Materials in Sustainable Energy

EU_JAPAN Expert ´s workshop on Critical Metals 21-11-2011

Oliver GutfleischLeibniz Institute for Solid State and

Materials Research, IFW Dresden, Germanyfrom 01.02.2012 @ Technical University of Darmstadt

AND Fraunhofer Group Substitutional Materials Hanau

� Materials for Energy Applications

� Magnetism and Energy:� Permanent magnets for E-mobility and wind turbines

� Rare earth metals, recycling

� Magnetocaloric materials for novel refrigeration tec hnology

� Description of structure, dynamics of phase transit ions and function on all length scales

Magnetic Materials in Sustainable Energy

Adv. Mat. (Review) 23 (2011) 821-842



Renewable Energy is intermittent in nature

SEASONAL CYCLE

LATITUDE

I

YEAR

I

DAY

I

DAY/WEEK

I

DAY - NIGHT CYCLE

Geographical ENERGY DISTRIBUTION of WWS

RESIDENTIAL Heat

STORAGE

TRANSPORT

MOBILITYWork

CONVERSION of WWS

CONVERSION into …

INDUSTRY Heat & Work

adapted from A. Züttel



Materials for sustainable energy

commodity materialsdisposible fuels

gas CH4oil CH 2

coal CH 0.8

heat useful work

combustion

sunlightwind water

geothermalbiomass

electricitybiofuel

hydrogenchemical fuel

useful work

Direct conversion

material + chemistryultra-small and -fast

modelling nano-science complex materials

BUT: critical metals



ENERGY CARRIERS

1

10

100

1000

10000

100000

0.001 0.01 0.1 1 10 100Energy density [kWh/kg]

Ene

rgy

dens

ity [k

Wh/

m3]

Pb-acidbattery

Li-ionbattery

mag. coil

EDLC comp. air

hot water

biomass

coal

oil

fusion

fission

hydrideshydrogenstorage

capacitor

hydro-power hydrogen

natural gas

flywheel

3

ultimatebattery

NH3

GRAVITATION

ELECTROSTATIC

NUCLEAR

CHEMICAL

ELECTROCHEMICALINERTIA

A. Züttel et al. , Phil. Trans. R. Soc. A (2010)



Permanent magnets for e-mobility and wind turbines

simulation

thermomechanicaltreatment

Characterisation with atomic resolution

grain boundary engineering

raw materialsrecycling

texturemicrostructure

stability

magneticinteraction



Intrinsic and extrinsic magnetic properties

saturation polarisation, Js

anisotropy field, Ha

Curie temperature, TC

intrinsic properties

microstructure

100µm > l > 1nm

↔ fit µ-magnetic length scales

+

dc: critical single-domain particle size

δδδδwδδδδw: domain wall width

remanence, Jr

coercivity, Hc

energy density, (BH)max

extrinsic properties⇒

J or B

Jr or Br

Hc

Hc

compound T C , K µ0Ms, T K1, MJ/m 3 dc, nm δδδδw

Nd2Fe14B 585 1.60 5 214 4

SmCo5 993 1.05 17 1700 3.7

Sm2Co17 1100 1.30 3.3 490 8.6

α-Fe 1043 2.16 0.046* 7 30

J. Phys. D: Appl. Phys. 33 (2000) R157-R172



Sintered NdFeB magnets for electro motors� Design light-weight, high torque-to-weight ratio mo tors , using

permanent magnets with adequate temperature stability

�� torque scales linearly with remanence

Adv. Mat. (Review) 23 (2011) 821-842

Courtesy: Toyota Motor Corporation



-4 -2 0 2 4-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

pola

risat

ion

J (T

)

applied field µ0H (T)

Texture in NdFeB sintered magnets

Nd Fe B

macrotexture ↔ microtexturemagnetic measurements ↔ Kerr microscopy

Nd2Fe14B

5µm



Magnetisation reversal in sintered NdFeB

200 nm

efficient use of Dy bygrain boundary diffussion process

coating

the weak link

Nd2Fe14B (Φ)

Nd1.1Fe4B4 (η)Nd2O3pore

5µmNd-rich intergranular phase

Hc = HA

Perfect materials: Coherent rotation

H

K

Hc << HA

Defects :Nucleation + propagation

activation volume

K

Nucleation-type magnet

crystalline or amorphousmetallic or oxidic

FM or PMmicrochemistry, structural defects

continuous or discontinuous



Atom model Simulated image Real image

Fe, Nd, B

10 Å

Nd2Fe14B <001>

Nd2Fe14B <001>

Sample thickness: 15 nm

- Nd2Fe14B, zone axis: <1-40>

1Å resolution by C s aberration corrected HRTEM

Nd Fe B

Multiscale characterisation III



Atomistic simulation of Nd-rich phase / Nd2Fe14B interface

[110]

[1-10]

[120]

[210]Nd2O3-hP5

Nd2Fe14B

Fourier enhanced HR-image

�� Thickness of region with reduced anisotropy varies with phase and orientation

Distorted region

Appl. Phys. Lett. 97 (2010) 232511, cooperation Uni Sheffield

Magnetoelastic anisotropy as function of distance for Nd2Fe14B (100) surface cut, c-axis parallel to interface to a fcc Nd (011) surface, the plane orientation is in respect to the interface. Inset: Top layer is the fcc Nd rich phase, bottom layer is the Nd2Fe14B phase.



� The motor/generator in a hybrid electric vehicle contains 2 kg of NdFeB . This application is set to grow to between 10million and 20million vehicles by 2018.(now: 2.5 out of 850 million vehicles are hybrids worldwide)

� New designs of wind generators use NdFeB magnets at a rate of ~700 kg per mega-watt . This application alone has potential to increase RE demand by 25% per year above current production.

� Hard disc drives cannot function without RE permanent magnets. Formerly 70% of the NdFeB market this is now diluted by the other major applications.

� World production of sintered NdFeB in 2011: ~100.000 t

� Solid state energy efficient cooling: Magnetocalorics

Permanent Magnet Growth



References in Adv. Mat. (Review) 23 (2011) 821-842

Installed wind power doubles every three years…



Rare Earth Minerals

Science News, August 27, 2011



Science News, August 27, 2011

Rare Earth Elements in Automotive



Pr, 6.60%

Ho-Tm-Yb-Lu, 0.00%

Y, 20.00%Er, 1.80%

Dy, 3.60%

Tb, 0.60%

Sm, 5.20%

Gd, 4.80%

Eu, 0.70%

Ce, 1.90%

La, 30.40%

Nd, 24.40%

Rare earth oxides in China

Southern Clay

Baotou & Shandong:

Light RESichuan

Area: Light RE

Southern China:

Heavy RE

Pr, 5.10%

Ho-Tm-Yb-Lu, 0.80%

Y, 0.20%Er, 0.01%Dy, 0.01%

Tb, 0.01%

Sm, 1.20%

Gd, 0.70%Eu, 0.20%

Ce, 50.07%

La, 25.00%

Nd, 16.70%

Baotou Bastnasite



$-

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$U

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G

Jan-07 Feb-07Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Nov-07 Dec-07 Jan-08 Feb-08Mar-08 Apr-08 May-08Jun-08 Jul-08 Aug-08 Sep-08 Oct-08 Nov-08Dec-08 Jan-09 Feb-09Mar-09 Apr-09 May-09Jun-09 Jul-09 Aug-09 Sep-09 Oct-09 Nov-09Dec-09 Jan-10 Feb-10Mar-10 Apr-10 May-10Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10Dec-10 Jan-11 Feb-11

Nd Metal $28 $28 $28 $31 $37 $45 $45 $44 $34 $35 $35 $34 $32 $36 $39 $37 $34 $32 $31 $26 $23 $22 $20 $15 $15 $15 $15 $16 $15 $15 $17 $18 $18 $22 $23 $26 $31 $31 $34 $35 $35 $38 $42 $44 $47 $51 $50 $51 $62 $74

Pr-Nd Metal $27 $27 $28 $29 $34 $43 $43 $39 $31 $30 $30 $29 $27 $31 $32 $31 $29 $29 $28 $23 $21 $21 $19 $13 $13 $13 $14 $14 $14 $14 $16 $16 $16 $21 $21 $24 $29 $29 $32 $33 $33 $35 $37 $39 $41 $43 $42 $42 $49 $60

Raw Materials: Nd and Pr-Nd metal (Asian Metal and metal-pages)

$/kg

50

30

10

2007 2008 201120102009

International Herald Tribune, May 4, 2011„rare earths prices skyrocket“

Nd 283 $/kg, Sm 146 $/kg, Dy 900 $/kg470 $/kg



UK Magnetics Society Newsletter Cover Winter 2010 Science News, August 27, 2011



• Meeting in 09/2010 at the German Ministry for Environment, a priority list for critical materials was determined. First Priority was given to:

• Dy• Nd• Tb• Pr• Ga (Magnets 0.1%, Power Electronics, DC/AC Converter)• In (Heating/Cooling, Electronics, Displays)• Pd (Fuel Cell, Cat., Power Electronics, Battery-Management-System)• Pt (Fuel Cell, Cat., Power Electronics, Battery (Au-Pt Cat. In Li-Air Batt.))• Au (Fuel Cell, Cat., Power Electronics, Battery (Au-Pt Cat. In Li-Air Batt.))• Cu (Electronics, Cables, Battery, Cooling/Heating,…)• Ru (Semi-Conductors, Capacitor, Fuel Cell, Battery) – all in mg volumes

• Dy was described to become the most critical element of all because of single source in the Chinese region and extremely low content in the mines of Molycorp and Lynas.

• After 2014 a sufficient amount of RE (beside Dy) ca n be expected in the global market.

• Dy will NOT suffice !

Rare metals in electro mobility



Recycling of scrap sintered NdFeBby hydrogen processing

(1) HD – hydrogen decrepitationand

(2) HDDR – hydrogenation disproportionationdesorption recombination

Issues

• Removal of brittle intermetallics imbedded with epoxy in assemblies

• Powders are very reactive

• Organics from machining, coatings and epoxies

• Coatings (e.g. Ni) for corrosion protection



HDDR

Nd2Fe14B + ½ xH 2 ⇔⇔⇔⇔ Nd2Fe14BHx ± ∆∆∆∆H1 (HD)

Nd2Fe14B + (2±x)H2 ⇔⇔⇔⇔ 2NdH2±x + 12Fe + Fe2B ± ∆∆∆∆H2

0.03 –0.13 MPa

H2

vac.5 kPa

H2

T

t

d-HDDR

T

pNdNdNdNd2222FeFeFeFe14141414BHBHBHBHxxxx NdHNdHNdHNdHxxxx

FeFeFeFeFeFeFeFe2222BBBB

texture memory effect texture memory effect texture memory effect texture memory effect Br >> Js/2

100 µm 300 nm

Hydrogen decrepitationHydrogen decrepitationHydrogen decrepitationHydrogen decrepitation



after HD after d-HDDR

Polyhedron single crystal particle ultrafine grained structure ～～～～300nm

Morphology of hydrogen recycled magnet

139.5

1.93

0

20

40

60

80

100

120

140

160

10 30 50 70 90 110 130

Hydrogen Pressure /kPa

BH

max

/kJ/

m3

0.0

0.5

1.0

1.5

2.0

2.5

μ0Hc /T

BHmax

μ0Hc



Weight: 465 gVolume: 110 cm 3

Motor power: 50 WMagnet weight : 80g

Weight: 295 g ( -37%)Volume: 54.5 cm 3 (-51%)Motor power: 50 WMagnet weight : 20g

conventional seat motorusing ferrite magnet

new seat motor usinganisotropic polymer bonded

HDDR magnet

Energy saving by size reduction

photos courtesy Aichi Steel

latest motor usinganisotropic polymer bonded

HDDR magnet

Weight: 140 g ( -53%)Volume: Motor power: 50 WMagnet weight : 8g

Adv. Mat. (Review) 23 (2011) 821-842



PATH 1 – use of existing phases

• Dy-less magnets – GBDP, grain refinement, interfacial control

• Textured nanocomposites (bottom-up approaches incl. the consolidation of nanoparticles, core-shell particles, etc)

� Reduction, Substitution and Recycling of RE-TM magn ets, reduce losses

on-going cooperations between us and Japanese partne rs

PATH 2 – “new” better “alternative” phases

• Search for new phases (Heusler, Mn3Ga, MnBi, Fe16N2, etc)

• FeCo (or similar, induce tetragonality or other lower symmetry, explore shape anisotropy)

• from metastability to volume samples

�� Aim to be (much) better than best hard ferrites wit h good thermal stability but without RE

How to move forward ?



180 200 220 240 260 280

0

5

10

15

20

25

30

35

0 ~ 5 T

LaFe12Si LaFe11.8Si1.2

LaFe11.57Si1.43

LaFe11.4Si1.6

LaFe11.2Si1.8

|∆S

| (J/

kg K

)

T (K)

Solid state energy efficient magnetic cooling

compact, solid state, silent and energy efficient heat pump

10 µm

Magnetic Materials and Devices for the 21 st Century: Stronger, Lighter, and More Energy Efficient

Adv. Mat. (Review) 23 (2011) 821-842



All refrigeration technologies have one thing in common: they contain a refrigerant which changes state, and in doing so, changes temperature. The changes in temperature of the refrigerant are relayed to the body to be cooled by means of one or more heat exchangers.

Magnetic refrigeration is the only alternative tech nology which would simultaneously eliminate the need for harmful refri gerant gases and reduce the energy requirements, and hence carbon dioxide e missions.

2 www.coolchips.gi3 www.coolchips.gi, www.healthgoods.com4 F.J. DiSalvo, Science, 285 703 (1999) and references therein5 D.L. Gardner and G.W. Swift, J. Acoust. Soc. Am., 114 1905 (2003)6 C. Zimm et al., Adv. Cryog. Eng. 43 1759 (1998)

Solid state energy efficient magnetic cooling



Magnetocaloric effect & Magnetic refrigeration

T

H

T+∆∆∆∆Tapply field

TT-∆∆∆∆T

expel heat �”isothermal”

H

remove field

∫

∂∂=∆

H

0 Hm

dHTM

S

dHT

M

C

TT

H

0 pH,pH,∫

∂∂−=∆

Large H

Large HT

M

∂∂

Small CH,p

Large MCE

adiabatic

adiabatic

� Maxwell equation applies to equilibrium thermodynam ics� δδδδM / δδδδT finite or infinite during a first-order magnetic phase transition ?� hysteresis � coupled magnetostructural transitions and related l atent heat� comparison with c p (H) measurements

absorb heat



RCP = B(M2-M1) per refrigeration cycle

Relative cooling power RCP

Actual cooling power [W/m 3]:RCP x operating frequency fInertia of heat exchange � upper limit 200 Hzanddynamics of the 1st-order phase transition

with M 2 > M1and ∆∆∆∆T (S1-S2) = B(M2-M1)

Magnetic refrigerant undergoing a 1st phase transition:(a) free energies of the two phases in the absence of magnetic field(b) field-induced entropy change plotted against T.

Phys. Rev. B 76, 092401 (2007)APL 90, 251916 (2007)Cooperation with IFW theory group M. Richter



Requirements and Challenges

� strong temperature dependence of magnetisation, large entropy jump at T C, large field dependence of T C

� large ∆∆∆∆Tad / ∆∆∆∆H �� driven by moderate magnetic field (RPMs) at a tailored operating temperature

� small thermal and magnetic hysteresis, dynamics

� material cost (e.g. Gd), non-toxic (e.g. As)

� high thermal and small electrical conductivity

� mechanical and chemical stability, high ductility



alloy Tc (K) structure ∆V problems

Gd5(Si1-xGex)4 130-270 orthorhombic⇔monoclinic

0.5 % high purity Gd

Giant magnetocaloric materials

Pecharsky and Gschneidner Jr., PRL 78 (1997) 4494

Gd5Si2Ge2 0 - 5 T

Gd 0 - 5 T

Gd 0 - 2 T

Gd5Si2Ge2 0 - 2 T



alloy Tc (K) structure ∆V problems

Gd5(Si1-xGex)4 130-270 orthorhombic⇔monoclinic

0.5 % high purity Gd

La(Fe,Si) 13Hxalso Si or Co

200-330 cubic �� cubic(NaZn13)

1.5 % αααα Fe

MnFe(P,As)MnFe(P,Ge)

150-340250-580

hex � hex(Fe2P)

0.1 % toxic

MnAsMn(As,Sb)

317reduced hysteresis

hex � ortho(NiAs�MnP)

2.2%0.7 %

toxic

Ni55.2Mn18.6Ga26.2

NiMnInCo315

various

L21 ⇔ 5Mmartensitic trans.

0 large strain,hysteresis

Giant magnetocaloric materials

3d intermetallic compounds as an alternative to heavy rare earths containing compounds ??(high abundance, relatively high magnetic moment, coupling to lattice)

in red: research @ IFW Dresden



La(FeSi)13

La: 8a sites Fe/Si: 8b and 96i

NaZn13-type structure stabilised by Si or Al

−)3( cFm

(1) What is special about La(Fe,Si) 13

(2) Synthesis

(3) Tailoring hysteresis and operating temperature

(4) Magnetovolume, hybridisation and cooling power

(5) Strain related effects

(6) Layered beds

Research @ IFW Dresden



La(Fe,Si)13Hx

Hydrogen insertion

• Tc ↑↑↑↑• 1st order transition preserved – large ∆∆∆∆Smax

Co substitution

• Tc ↑↑↑↑• gradual transition to 2nd order – ↓↓↓↓ ∆∆∆∆Smax

J. Magn. Magn. Mat. 320 (2008) 2252

JAP 102 (2007) 053906

Tailoring Tc by interstitial hydrogen



∆∆∆∆Tad and ∆∆∆∆V/V of LaFe 11.7Si1.3

160 165 170 175 180 185 1900

1

2

3

4

5

6

7

∆V/V

, %

∆Tad

, K

T,K

LaFe11.7

Si1.3

µ0H=1.9T

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

adiabatic temperature change and related magnetovol ume effects



New porous morphology of LaFe 11.6Si1.4

BulkHP @ 625°CHP @ 575°C

Hot pressed porous compacts retain mechanical integ rity during temperature-field cycling

Adv. Mat. 22 (2010) 3735, Patent filed.



180 200 220 240 260 280 300 320 3400

1

2

3

4

5

6

7 µ0H = 1.9 T

LaFe11.74

Co0.13

Si1.13

LaFe11.40

Co0.52

Si1.09

LaFe11.05

Co0.91

Si1.04

LaFe10.71

Co1.30

Si1.00∆T

AD, K

Temperature,K

LaFe11.6

Si1.4

260 270 280 290 300 310 320 330 340 3500

1

2

3

4

5

La(FeSi)13

HX

µ0H = 1.9 T

LaFe11.05

Co0.91

Si1.04

LaFe10.71

Co1.30

Si1.00

∆TA

D, K

Temperature,K

Gd

Comparison of ∆∆∆∆Tad

1st vs. 2nd order type materialsEU project SSEEC, cooperation Vacuumschmelze Hanau

�� comparison in a realistically operating prototype d evice

refrigerant capacity



Towards applicationPrototype development in the SSEEC project (EU)

15 K span with single alloy35 K span with multi-alloyregenerator achieved

Plates of sintered La(FeCoSi) 13 of 0.25mm thickness

produced by Vacuumschmelze Hanau /System by Camfridge Ltd.

and 1.2 Tesla



Generally, we have a number of parameters to maximize the MCE at a given magnetic field:

• Lattice (especially for low magnetic fields the way forward is to maximize the structural contribution; big shift of the magnetostructuraltransition with field (several Kelvin per Tesla))

• Spins (exploit chemical complexity to precisely tune magnetism)

• Hysteresis (maintain first-order character but minimize hysteresis)

• µ-structure (engineer (multiphase) nanostructure with stress generating/relieving features)

• Metastability and non-equilibrium (coexistence)




Drastically Reduced Rare Earth use in Applications of Magnetocalorics

• minimise rare earth wastage through the efficient manufacture of large volumes of magnetocaloric material parts;

• drastically reduce the consumption of rare earth permanent magnets in end use through step-change improvements in the performance of magnetocaloric materials;

• investigate the fundamental properties of several rare earth-free magnetocaloric materials through theoretical modelling, resulting in improved understanding of magnetocaloric mechanisms and parallel benefits for thermomagnetic power generation.




October 2011



Abundance of rare earths



Rare earth value chain

Courtesy P. Dent, MMM Conf. Nov. 2011



Manufacturing of sintered RE magnets

Courtesy P. Dent, MMM Conf. Nov. 2011

magnetic materials in sustainable energy · rare earth metals, recycling magnetocaloric materials...

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