Leibniz-Institut for
Solid State and
Materials Research
Dresden
High temperature
superconductors:
Properties and applications
Ruben Hühne
IFW Dresden
Institute for Metallic Materials
Superconducting Materials Group
1
Outline
• High temperature superconductors (HTSC)
Introduction
which materials?
what are the basic properties?
• Power applications of HTSC
what are possible applications?
what are the requirements for application?
• Development of conductor based on HTSC
Powder-in-tube technology (PIT)
YBCO coated conductors
• textured substrates: RABiTS
• textured buffers: IBAD
2
1
Basic properties of HTSC
Outline
• High temperature superconductors (HTSC)
which materials?
what are the basic properties?
• Power applications of HTSC
what are possible applications?
what are the requirements for application?
• Development of conductor based on HTSC
Powder-in-tube technology (PIT)
YBCO coated conductors
• textured substrates: RABiTS
• textured buffers: IBAD
3
Superconductivity
Liquification of Helium
H. Kamerlingh Onnes, Leiden (1908)
Discovery of „Superconductivity“: ideal conductivity
Kamerlingh Onnes
H. Kamerlingh Onnes, Leiden (1911)
Many metals become superconducting at low temperatures
Temperature (K)
Basic properties of HTSC
Discovery of Superconductivity
Liquid hydrogen: 20 K
Year of discovery
Step in the electrical resistivity of Hg:
critical temperature TC
4
Current transport without losses possible
Cooling with liquid helium necessary
2
Basic properties of HTSC
High temperature superconductors
77 K
Ba-La-Cu-O compound:
J. G. Bednorz, K. A. Müller, Z.
Physik, B 64 (1986) 189
Ba-La-Cu-O
Cooling with liquid nitrogen possible
compound
commercial
potential
5
TC (K)
YBa2Cu3O7-δ
Y-123
Bi2Sr2CaCu2O8
Bi-2212
84
Bi2Sr2Ca2Cu3O10
Bi-2223
110
TlBa2Ca2Cu3O10
Tl-1223
125
HgBa2Ca2Cu3O10
Hg-1223
133
92
High temperature superconductors
Bi(Pb)-2212
REBCO
REBa2Cu3O7-x
RE: Y, Nd, Er, Gd, Eu…
Bi(Pb)-2223
2212 ≈ (Bi,Pb)2Sr2CaCu2Ox (x ≈ 8)
2223 ≈ (Bi,Pb)2Sr2Ca2Cu3Ox (x ≈ 10)
O
CuO2-planes
responsible for
superconductivity
Ba
Y
Properties show
high anisotropy
Ca
Bi
Sr
Cu
O
6
Cu
Ceramics: layered
perovskite material
(2-dimensionality)
c = 11.68 Å
Basic properties of HTSC
BiSCCO
TC = 85 K
TC = 110 K
b = 3.88 Å
a = 3.83 Å
TC = 92 K
3
High temperature superconductors
Dependence of the superconducting
properties on O doping
Basic properties of HTSC
Anisotropy of the resistivity
7
HTSC in magnetic fields
8
superconductor
type II
nc
µ0HC2 (T)
µ0H (T)
Basic properties of HTSC
B(T) phase diagramm of type II superconductors
sc
Mixed phase
(Shubnikov)
Meissner
phase
magnetic field
TC
µ0HC1 (T)
flux line
T (K)
type II TC (K)
µ0HC2 (T)
9.3
0.3
Nb3Sn
18.0
24.5
Nb3Ge
23.2
38.0
MgB2
39.0
17.0
Y-123
92.0
150
Bi-2223 110.0
108
Nb
Φ0
normal
conducting core
penetration
depth λ
shielding
currents
Cooper pair
density n
flux quantum
-15
2
F 0 = 2 ·10 Tm
magnetic field B
r
vortex
coherence lenghth ξ
4
HTSC in magnetic fields
HTS
sc
µ0Hirr
µ0H (T)
Basic properties of HTSC
B(T) phase diagram of superconductors: critical fields
nc
vortex
liquid
vortex
glass
µ0HC2
vortex
lattice
applied magnetic field penetrates the
superconductor in form of vortices
µ0HC1
current leads to Lorenz force on vortex
lines
movement of vortices leads to
dissipation: Irreversibility line
pinning of the vortices necessary for high
critical currents in magnetic fields
incorporation of nanoscaled pinning
centres
T (K)
Φ0
pointlike
pinning
centers
9
core diameter ~ 2ξ
vortex
HTSC in magnetic fields
Basic properties of HTSC
Irreversibility line
Properties of the vortices are dependant
on the crystal structure of the material
Bi-2223
YBCO
BSCCO-2223
YBCO
CuO2
d
CuO2
CuO2
CuO2
CuO2
YBCO is the preferred
material for applications
at 77 K in higher
magnetic fields
d
CuO2
CuO2
CuO2
CuO2
CuO2
CuO2
CuO2
d~ 2ξ
10
CuO2
CuO2
B
3D flux line
d > 2ξ
2D pancake vortices
5
Critical current density
Basic properties of HTSC
Current-voltage characteristic of superconductors
I 
U ( I ) = U 0  
 I0 
n
Critical current Ic is dependant on
temperature and magnetic field
Critical current density Jc:
Ic divided by cross section of the superconductor
Engineering current density Je:
11
Ic divided by cross section of complete conductor
Critical current density
Anisotropy
9
3x10
B = 1 T, φ = 0°
B = 4 T, φ = 0°
B = 1 T, φ = 90°
B = 4 T, φ = 90°
9
2x10
2
Jc (A/m )
Basic properties of HTSC
Critical current density
9
1x10
0
-90
12
-45
0
45
90
θ (°)
6
Basic properties of HTSC
HTSC grain boundaries
YBCO
Bi2212
Measurement
on bicrystals
Bi2223
Hilgenkamp et al., Rev. Mod. Phys. 74 (2002) 485
High Jc in polycrystalline materials require strong biaxial texture
13
HTSC grain boundaries
Θ
Basic properties of HTSC
Origin of Jc-limitation at grain boundaries:
Symmetry of the order parameter
Band bending due to interface
charging
d=b/2sin(Θ/2) ≈ b/Θ
d
Für b=0.38nm
Θ=8° ⇒ d=2.7nm
(100)
(100)
(010)
(010)
Depletion zone
KG
14
Microstructure:
• Strain fields around dislocations,
• Distorted areas in large angle grain
boundaries
Deviations from ideal stoichiometry
• regions with oxygen vacancies
• disorder
• localised states
Direct suppression of pairing
mechanism
Reason:
Extremly short coherence length
ξ and low charge carrier density
in HTSC
EL
Tcmax
TcKorn
0
EF
EV
λ TF
Tc
d λ TF
Hilgenkamp et al., Rev. Mod. Phys. 74 (2002) 485
7
Basic properties of HTSC
Other „new“ superconductors
MgB2
Fe-pnictides and -chalcogenides
Phase known since the early 50‘s
Superconductivity discovered 2008
Jones et al., J. Am. Chem. Soc. 76 (1954) 1434
Kamihara et al., J. Amer. Chem. Soc. 130 (2008) 3296
Superconductivity discovered in 2001
Nagamatsu et al., Nature 410 (2001) 63
Tc = 39 K: highest Tc for binary
superconductors
LaO1-xFxFeAs
GdO1-xFxFeAs
SmO1-xFxFeAs
Ba1-xKxFe2As2
FeSe1-xTex
…
Tc ~ 26 K
Tc ~ 53 K
Tc ~ 55 K
Tc ~ 38 K
Tc ~ 15 K
no weak link behavior at grain
boundaries in contrast to cuprates
15
large coherence length ξab = 7-10 nm
Applications of superconductors
Outline
• High temperature superconductors (HTSC)
which materials?
what are the basic properties?
• Power applications of HTSC
what are possible applications?
what are the requirements for application?
• Development of conductor based on HTSC
Powder-in-tube technology (PIT)
YBCO coated conductors
• textured substrates: RABiTS
• textured buffers: IBAD
16
8
Applications of superconductors
Application of classical superconductors
Application in medical and analytical devices
Medicine:
Magnetic Resonance
Imaging (MRI) of soft
tissues like organs,
cartilages, tendons etc.
>3000 t NbTi per year
Analytics:
Nuclear Magnetic Resonance
(MNR) spectroscopy
>500 t Nb3Sn per year
17
Applications of superconductors
Application of classical superconductors
Magnets for research devices
• Accelerators in particle physics
• Reactors for nuclear fusion
18
9
Applications of superconductors
Power applications of HTSC
Generator
Cable
Transformer
Higher current density lower weight @ same power
Lower losses / higher efficiency
Environmental friendly
Motor
copper
19
Applications of superconductors
Power applications of HTSC
Ship populsion motors
20
10
Applications of superconductors
Power applications of HTSC
Superconducting cable
350 m long cable at 34.5 kV and 800 A in real network
Made form BiSCCO and YBCO based conductors
21
Required properties for different power applications
Current limiter
106
Jc [A/cm²]
Applications of superconductors
Power applications of HTSC
Cable
Fusion magnets
105
MRI magnets
104
Transformers
NMR-Spectrometer
Typical YBCO
layer on technical
substrates at 77 K
10³
10²
5
22
Generators,
Motors
10
15
20
B [T]
11
Applications of superconductors
Application of HTSC
23
Main requirements on HTSL conductors for application
• Mechanical flexible conductor (for coils etc.)
metal-ceramic heterostructure
• High current transport capability at:
- highest application temperature (above 77 K)
- highest magnetic fields
strongly textured superconductors
defined incorporation of pinning centres
• Availability in long length
(several km necessary for demonstrators)
• Cheap production of long length necessary
robust and fast methods
low cost materials
• Other requirements for certain application:
- low ac-losses
- high mechanical strength
- reduced anisotropy
Preparation of HTSC conductors
Outline
• High temperature superconductors (HTSC)
which materials?
what are the basic properties?
• Power applications of HTSC
what are possible applications?
what are the requirements for application?
• Development of conductor based on HTSC
Powder-in-tube technology (PIT)
YBCO coated conductors
• textured substrates: RABiTS
• textured buffers: IBAD
24
12
Preparation of HTSC conductors
Powder-in-Tube (PIT) Technology
Preparation of BiSCCO and MgB2 conductors
Precursor
Mixture of
Base Compounds
•
Sol-gel methods
•
Mechanical
alloying
e.g Bi-Pb-Sr-Ca-Cu-O
powder
with Bi-2223
composition
or
Mg, B mechanically
alloyed
precursor
25
Deformation
Precursor
Thermal Treatment
Drawing
Ag Tube
Bundling
Drawing
Rolling
Cross section
Longitudinal Section
PIT conductors
Preparation of HTSC conductors
BiPbSrCaCuO (2223) PIT conductor
26
available in long length
moderate performance (Jc < 60kA/cm2)
not applicable in magnetic fields at 77 K
too expensive (Ag)
MgB2 PIT conductor
first long length available
potential application at ~ 20 K
(boiling point of hydrogen)
combined with hydrogen
technology
MgB2
Nb
Cu
CuNi
600 m long
BSCCO tape
MgB2 multifilamentary conductor
Cross section of BSCCO tape with 61 filaments
13
YBCO coated conductors
Advantage: high irreversibility
fields at 77 K
Challenge: grain boundaries
Bi-2223
77K
YBCO
6
10
2
J (A/cm )
5
10
c
YBCO coated conductors
Application of YBCO for HTSC conductors
Y123
4
10
0
4
8
12
16
GB angle (°)
• Powder-in-tube technology does not work for YBCO
• Long length of highly textured YBCO conductors required
27
Growth of epitaxial YBCO on a textured template:
template: coated conductors
Preparation of YBCO coated conductors
YBCO coated conductors
Major processing routes for YBCO coated conductors
Rolling Assisted Biaxially Textured
Substrates (RABiTS)
Ion Beam Assisted Deposition
(IBAD)
Rolling and
Annealing
Ion beam
Ni, Cu
PLD, Sputtering
Thermal evaporation
CVD,CSD
Based on biaxially textured substrates
PLD
e-beam
Sputtering
Based on biaxially textured buffer layers
28
14
RABiTS Approach
YBCO coated conductors
Rolling Assisted Biaxially Textured Substrates (RABiTS
(RABiTS))
29
Rolling
Recrystallization
Epitaxial Film
Deposition
Nickel
• Cold deformation >95% • Typical 900°C/1h
• Pure Ni
• Ar/H2-atmosphere
• Microalloyed Ni :
Ni-0.1at%Mn
• Alloyed Ni :
Ni-5at%W
Ni-7.5at%W
Ni-9at%W
Ni-9at%V
Ni-13at%Cr
• Composites :
Ni-W/Ni-Cr
Ni-W/Ni-W
• PLD
• E-beam
• Sputtering
• CVD
• CSD
(111)-pole figure of Ni-5at%W
Tape Processing I
YBCO coated conductors
Hot rolling
30
Induction furnace
Intermediate Ni bars
Final tape
(up to 100 m)
Special 4high mill
15
Tape Processing II
YBCO coated conductors
Continuous tape annealing
Process gas
Characterisation
Electron
backscattering
diffraction
(EBSD)
Exhaust
Tape
Exhaust
Tape
Heating zone
B
Heating zone
B
Heating zone
A
Reel
Gas
Reel, motorized
Gas
Continuous Tape Annealing
„Kikuchi pattern“
Local texture
information
„Texture maps“
31
YBCO coated conductors on RABiTS
YBCO coated conductors
Epitaxial deposition of buffer layers and YBCO
Necessary function of buffer layers:
• Suppression of Ni diffusion into YBCO
(Ni degrades superconductivity)
• Suppression of uncontrolled O diffusion to
substrate (may lead to cracks and peeling off)
• Texture transfer from substrate to superconductor
(cube textured YBCO)
(111)
Ni-5at%W RABiT substrate
YBCO
(103)
CeO2
YSZ
Y2O3
32
YBCO coated conductor
architecture
Ni
Cross section of coated conductor
YBCO layer
Hühne, R. et al., Supercond. Sci. Technol. 20 (2007) 709
16
YBCO coated conductors on RABiTS
YBCO coated conductors
Pulsed laser deposition - PLD
• high quality of layers
• flexible method
• small substrates (typical 10 x 10 mm²)
• vacuum equipment necessary
• high costs
thermo
couple
laser plume
target
substrate heater
laser beam
ideal for research and development
Chemical solution deposition - CSD
Starting material
as organic
compounds
dipcoating
heat treatment
• no vacuum necessary
• easily scalable on long length
• high yield achievable
• large coating areas possible
substrate
A
B
C
precursor
solution
ideal for industrial
processing
33
Preparation of YBCO coated conductors
YBCO coated conductors
Major processing routes for YBCO coated conductors
Rolling Assisted Biaxially Textured
Substrates (RABiTS)
Ion Beam Assisted Deposition
(IBAD)
Rolling and
Annealing
Ion beam
Ni, Cu
PLD, Sputtering
Thermal evaporation
CVD,CSD
Based on biaxially textured substrates
PLD
e-beam
Sputtering
Based on biaxially textured buffer layers
34
17
Ionenstrahlunterstützte Deposition (IBAD)
YBCO coated conductors
Principle:
Comparison to RABiTS approach
Substrate
Ionenstrahl
all kind of substrates possible
smaller grains and sharper textures
compared to RABiTS higher Jc
extremely fast texturing process for
IBAD-MgO or IBAD-TiN (within 10 nm!)
PLD
Evaporation
Sputtering
Target
complex process
smooth (polished) substrates
necessary
vacuum equipment and on-line
control necessary
Preparation of textured buffer
layers
Typical IBAD coated conductor
architecture Superpower Inc.
(USA)
35
Available in length of > 1 km
Ion-beam assisted deposition (IBAD)
YSZ, CeO2, Pr6O11, Gd2Zr2O7...
MgO, TiN…
Cube texture in 10 nm thick IBAD-layers on
amorphous substrates
35
in-plane orientation [°FWHM]
YBCO coated conductors
Materials for the IBAD process:
process:
IBALD-YSZ, 2,3 Å/s
additional epitaxial CeO2
IBALD-YSZ, 1,2 Å/s
additional epitaxial CeO2
30
25
Wang et al. APL 71 (1997) 2955
20
15
10
5
divergence of the ion beam
Betz (1998)
0
0
1
2
3
4
5
6
YSZ-thickness [µm]
Ion beam improves in-plane texture
through a growth selection process
Slow process
Ion beam influences already the
nucleation
Very fast process
36
18
Optimization of YBCO coated conductors
Reduction of ac-losses
• improvement of the critical current density
Jc in magnetic fields
• incorporation of nanosized pinning sites:
• non-superconducting particles
• growth defects through islands on
the substrate
• magnetic nanoparticles
development of RABiTS with
reduced ferromagnetism
• hysteretic losses in YBCO due to
conductor geometry
6
10
5
10
4
10
3
10
filamentation of conductors
MOD-YBCO 1.5 at.% Hf
MOD-YBCO 1 at.% Hf
MOD-YBCO 0.5 at.% Hf
MOD-YBCO
8
7
6
5
4
3
2
1
0
T = 77K
BIIc
0.15 mm
4 mm
0
2
4
6
8
10
magnetic field µ0H /T
0
37
• losses due to magnetization change
of ferromagnetic substrates
7
10
Pinning Force Density
9
³
Fp(10 N/m )
critical current density Jc [A/cm²]
YBCO coated conductors
Artificial pinning centres
2
4
6
magnetic field µ0H /T
8
Engel, S. et al., Appl. Phys. Lett. 90 (2007) 102505
• coupling losses in multilayer
systems
Summary
Summary
• HTSC are highly anisotropic, ceramic
superconductors
• HTSC are potential materials for different
applications using liquid nitrogen cooling
• Main challenge is to prepare flexible
conductors with high critical current
densities in higher magnetic fields on long
length
• Different approaches were developed to
realize such conductors:
Powder-in-tube technology
Coated conductors
38
19