Progress in research and development of IBAD-MOCVD based superconducting wires2010... ·...

Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010

Progress in research and development of IBAD-MOCVD based superconducting wires

V. Selvamanickam, I. Kesgin, A. Guevara, T. Shi, Y. Yao, Yue Zhang, Yangxin Zhang, and G. Majkic

University of Houston, Houston, TX, USA

Y. Chen, Y. Qiao, S. Sambandam, G. Carota, A. Rar, Y. Xie, and J. Dackow

SuperPower Inc., Schenectady, NY, USA

1

Partially supported by U.S. DOE Office of Electricity & Energy Reliability and CRADAs with Oak Ridge, Argonne, and Los Alamos National Laboratories, and National Renewable Energy Laboratory


Dedicated in memory of Andrei Rar, 1961 – 2010SuperPower’s Characterization Scientist

A invaluable member of SuperPower Organization


Superior wire features with IBAD-based substrates

2 µm Ag

20µm Cu

20µm Cu50µm Hastelloy substrate

1 µm YBCO - HTS (epitaxial)~ 30 nm LMO (epitaxial)

~ 30 nm Homo-epi MgO (epitaxial)~ 10 nm IBAD MgO

< 0.1 mm

• Use of IBAD as buffer template provides the choice of any substrate• Advantages of IBAD are high strength, low ac loss (non-magnetic, high resistive

substrates) and high engineering current density (ultra-thin substrates)• Fine grain size of superconductor on IBAD templates is very beneficial for

multifilamentary wires for low ac losses• Amorphous alumina barrier layer enables superconductor processing at higher

temperatures for high Ic.


MOCVD-based coated conductors are routinely produced in kilometer lengths

4

0

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0 100 200 300 400 500 600 700 800 900 1000

Crit

ical

Cur

rent

(A/

cm)

Position (m)

• Minimum current (Ic) = 282 A/cm over 1065 m • Ic × Length = 300,330 A-m

77 K, Ic measured every 5 m using continuous dc currents over entire tape width of 12 mm (not slit)

Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010 5

Wire price-performance is the key factor for commercialization• Today’s 2G wire : 100 A performance at 77 K, zero applied magnetic field,

Price $ 40/m = $ 400/kA-m

• At this price, cost of wire for typical device project (other than cable) > $ 1 M (more expensive than the typical cost of the device itself !)Cost of wire for a 500 km cable project = $ 20 M (~ cost of cable project itself !)

Metric Today Customer requirementPrice $ 400/kA-m < $ 100/kA-m* For commercial market entry

(small market)< $ 50/kA-m* For medium commercial market< $ 25/kA-m* For large commercial market

*at operating field and temperature

Four to 15-fold improvement in wire price-performance needed !


Objectives of UH-SuperPower program focused on meeting wire price-performance metrics• Higher self-field critical current in 2G wire by increasing film thickness

– HTS is still only 1 to 3% of 2G wire compared with 40% in 1G wire and is the only process that needs to be changed in 2G wire for high Ic.

• Significantly modify in-field critical current performance of 2G wire– Maximize potential of rare-earth, dopant, nanostructure modifications to

tailor in-field critical current in device operating conditions• Reduce wire cost by high efficiency, simpler processes

– Silver electrodeposition instead of sputtering– Substrate planarization instead of electropolishing + buffer– Improved MOCVD precursor conversion efficiency (only 15% now)

• Reduce wire cost by increased yield– Develop new and enhanced on-line QA/QC tools

• Added value to customer with advanced wire architectures– Multifilamentary wire for low ac loss


Improved pinning by Zr doping of MOCVD HTS wires

Process for improved in-field performance successfully transferred to manufacturing

0.2

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1.0

1.2

1.4

1.6

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-30 0 30 60 90 120 150 180 210 240 270 300 330 360J c

(MA

/cm

2 )

Crti

ical

cur

rent

(A/1

2 m

m)

Angle between field & tape normal (°)

0% 2.5% 5%

7.50% 10% 12.50%

1.0 T, 77 K

• Systematic study of improved pinning by Zr addition in MOCVD films at UH.• Two-fold improvement in in-field performance achieved !

10

20

30

40

0 30 60 90 120 150 180 210 240

Crit

ical

cur

rent

(A/4

mm

)

Angle between field and c-axis (°)

Standard Production wire

Enhanced Zr-doped production wire

c-axis


Enhanced in-field performance of Zr-doped wires transitioned to long lengths

0

10

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60

0

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

I cat

0.5

2 T

(A/ 4

mm

wid

th)

Position (m)

Standard undoped wire, self-field Ic

Zr-doped wire self-field Ic

Standard undoped wire, B || c-axis

Standard undoped wire, min Ic angle

Zr-doped wire, B || c axis

Zr-doped wire min Ic angle

Self-

field

I c(A

/ 4 m

m

• Even with 16% lower self-field Ic, Zr-doped wire exhibits 80% higher Ic at B || c, and 71% higher Ic at min Ic angle compared with standard wire

• Very uniformity of in-field Ic over 130 m of Zr-doped wire (~ 3%)


Benefit of Zr-doped wires realized in coil performance

Coil properties With Zr-doped wire With undoped wire

Coil ID 21 mm (clear) 12.7 mm (clear)

Winding ID 28.6 mm 19. 1 mm

# turns 2688 3696

2G wire used ~ 480 m ~ 600 m

Wire Ic 90 to 101 A 120 to 180 A

Field generated at 65 K 2.5 T 2.49 T

Same level of high-field coil performance can be achieved with Zr-doped wire with less zero-field 77 K Ic, less wire and larger bore


2010 effort on Zr-doped MOCVD wires• In 2009, we fixed the HTS film composition at Y0.6Gd0.6-Ba-Cu-O (based

work on undoped compositions) and found optimum Zr doping to be 7.5%.

In 2010, we sought to determine

• If there is a rare-earth combination and content that works better with Zr-doped MOCVD wires (most BZO literature is on pure Y or pure Gd)

Fixing Zr dopant level at 7.5%, we investigated• influence of HTS film thickness• influence of Y : Gd ratio with a fixed (Y+Gd)

value• influence of Y+Gd value at a fixed Y:Gd ratio

Precursor is maintained at ambient conditions outside deposition chamber and numerous combinations can be studied in a single run.


Improvement with Zr in thicker films

Improvement in in-field critical current of Zr-doped wires increases with film thickness

20

70

120

170

60 90 120 150 180 210 240 270 300

Crit

ical

cur

rent

(A/1

2 m

m)


0% Zr, 1 pass 7.5% Zr, 1 pass

1.0 T, 77 K

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140

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60 90 120 150 180 210 240 270 300

Crit

ical

cur

rent

(A/1

2 m

m)


0% Zr, 2 passes 7.5% Zr, 2 passes

1.0 T, 77 K

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60 90 120 150 180 210 240 270 300

Crit

ical

cur

rent

(A/1

2 m

m)


0% Zr, 3 passes 7.5% Zr, 3 passes

1.0 T, 77 K

All samples were of composition Y0.6Gd0.6BCO


Improvement in in-field critical current of Zr-doped wires increases with

thicknessCritical current at 1 T (A/12 mm)

1 pass max near B || c min Ic max near B || a-b0% Zr 43 32 857.5% Zr 82 39 71Improvement 91% 22% -16%

2 passes0% Zr 65 43 1067.5% Zr 130 67 112Improvement 100% 56% 6%

3 passes0% Zr 77 53 1287.5% Zr 177 92 151Improvement 130% 74% 18%


Influence of Y:Gd ratio

Improved Ic retention at low fields, B || c (< 0.5 T) with decreasing Y:Gd ratio

00.20.40.60.811.2

012345

050

100150200250300350

0 0.2 0.4 0.6 0.8 1 1.2

Gd content

J c(M

A/c

m2 )

Crit

ical

cur

rent

(A/1

2 m

m)

Y content

• All samples made in one run with 7.5% Zr.• Y+Gd maintained at 1.2 but ratio of Y:Gd

changed from 1.2:0 to 0:1.2 in steps of 0.2

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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6J c

(MA

/cm

2 )

Crit

ical

cur

rent

(A/1

2 m

m)

Magnetic Field (T)

Y1.2Gd0.0Y0.8Gd0.4Y0.6Gd0.6Y0.2Gd1.0Y0.0Gd1.2

B || c, 77 K

0.0

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1.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

I c/

I c(B

= 0

)

Magnetic Field (T)

Y1.2Gd0.0Y0.6Gd0.6Y0.2Gd1.0Y0.0Gd1.2

B || c, 77 K


Influence of Y:Gd ratio

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60 90 120 150 180 210 240 270 300

Crit

ical

cur

rent

(A/1

2 m

m)


Y1.2Gd0.0 Y1.0Gd0.2 Y0.8Gd0.4

Y0.6Gd0.6 Y0.4Gd0.8 Y0.2Gd1.0

Y0.0Gd1.2

1.0 T, 77 K

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I c/

I c(B

= 0

)


Y1.2Gd0.0 Y1.0Gd0.2 Y0.8Gd0.4Y0.6Gd0.6 Y0.4Gd0.8 Y0.2Gd1.0Y0.0Gd1.2

1.0 T, 77 K

• Increasing Ic in the vicinity of B || a-b with decreasing Y:Gd ratio while Ic in the vicinity of B || c is constant at 25 to 30% retention

• Higher minimum Ic with decreasing Y:Gd ratio


5 nm

BZO epitaxial particle

BZO (111) particles BZOrod

Y1.2Gd0 Y0Gd1.2

Additional defect structure in Gd1.2BCO wires for better B || wire pinning

BZO (111) particles along a-b plane in Gd1.2BCO

TEM by C. Cantoni & A. Goyal, ORNL


4 105

6 105

8 105

1 106

1.2 106

1.4 106

-50 0 50 100

Gd1.2Y1.2Y0.6Gd0.6

Angle [deg]

65K, 5T

Influence of Y:Gd changes at lower temperatures

• Best in-field performance switches from Gd1.2 to Y1.2 composition with decreasing temperature

• Higher Tc of Gd1.2 composition could be a reason

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y = 88.893 + 2.9645x R= 0.97963

Y1.2-x

Gdx

Measurements by Y. Zuev and A. Goyal, ORNL


Influence of Y+Gd content• 7.5% Zr in all samples• Y content = Gd content• Y+Gd content varied

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60 90 120 150 180 210 240 270 300

Crit

ical

cur

rent

(A/1

2 m

m)

Angle between magnetic field and c-axis ( )

Y0.65Gd0.65 Y0.7Gd0.7 Y0.75Gd0.75 Y0.8Gd0.8

1.0 T, 77 K70

90

110

130

250

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330

350

1.2 1.3 1.4 1.5 1.6 Icat

1 T

, ||

to ta

pe (A

/12

mm

)

zero

-fie

ld I c

(A/1

2 m

m)

Y + Gd content

Critical current can be tuned in desired orientation of magnetic field in application by modifying total rare earth content even with a fixed Zr % !


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0.2

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70 75 80 85 90 95 100 105

I c/

I c(B

=0)

Angle beteweend field and c-axis (°)

(Y,Gd)1.2 (Y,Gd)1.3 (Y,Gd)1.4 (Y,Gd)1.5

1.0 T, 77 K

Thicker (Gd,Y)2O3 precipitates along a-b plane in high (Gd,Y) wires

TEM by Dean Miller, ANL


In-field performance of Zr-doped films is drastically modified by rare earth content

Zr content maintained at 7.5% in all three samples

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Crit

ical

cur

rent

(A/1

2 m

m)


Y0.6Gd0.6 (Y,Gd)1.5 Y1.2

1.0 T, 77 K

c-axis

Fewer defects along a-b plane in Y1.2 ; defects prominent along a-b plane in (Y,Gd)1.5

Y1.2

20 nm

(Y,Gd)1.5


Superior performance in recentZr-doped MOCVD production wires

Zr-doped production wires with new composition exhibit significantly improved critical current at 4.2 K in high magnetic fields up to 30 T !

Measurements by V. Braccini, J. Jaroszynski, A. Xu,& D. Larbalestier, NHMFL, FSU

T, K

0 20 40 60 80

Jc, M

A/cm

2

0

10

20

30

40

50

60 Production wire1.1 µm thick HTS filmIc (77 K, 0 T) = 310 A/cm

1 10

100

1000

T=4.2K

I c - 4

mm

wid

th (A

)

B (T)

undoped, B perp. wire undoped, B || wire FY'09 Zr-doped, B perp. wire FY'09 Zr-doped, B || wire FY'10 Zr-doped, B perp. wire FY'10 Zr-doped, B || wire

Zr-doped wires with optimized rare-earth content transferred from R&D at Houston to SuperPower production operation.

http://www.fsu.edu/


Substantial improvement in 2010• 2009 : 28% self-field retention in Ic at 77 K, 1 T, B ⊥ wire in R&D wires

2010 : Achieved 39% retention in R&D wire. • Zr-doped MOCVD process fully transitioned to production and is

routinely produced in kilometer lengths: now a standard product offering by SuperPower (‘ AP: Advanced Pinning’ wire)• 2010 : 25 – 30% self-field retention in Ic at 77 K, 1 T, B ⊥ wire routine in

production wires• 55 to 65% improvement in Ic over 2009 Zr-doped production wire at high

fields

0%

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100%

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Zero

-fie

ld I c

rete

ntio

n

Crit

ical

cur

rent

(A/1

2 m

m)

Magnetic Field (T)

B ⊥ wire, 77 K

39% retention at 1 T !

Jc @ 4.2 K in field (A/4 mm)

FY’09 FY’10*

10 T, B ⊥ wire 201 310

20 T, B ⊥ wire 118 183

5 T, B || wire 1,219 1,893

10 T, B || wire 1,073 1,769

* Jc = 50 MA/cm2 at 4.2 K, 0 T


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100,000

2004 2005 2006 2007 2008 2009 2010

Pric

e ($

/kA

-m)

Year

77 K, self field

30 K, 2 T

Rapidly decreasing price of 2G HTS wire through technology advancements

10 m demo

100 m demo

First year of pilot production

2 to 4x higher throughput

Creation of separateManufacturing andR&D facilities

500 m demo 1,000 m

demo

AP wire (Zr-doped) product introduction

Wire price-performance improved by ~ 200% to ~ $ 100/kA-m for 30 K, 2 T applications


Goals for wire performance improvements• Two-fold improvement in in-field performance achieved with Zr-doped wires• Further improvement in Ic at B || c : Now 30% retention of 77 K, zero field value at

77 K, 1 T ; Goal is 50%.• Improvement in minimum Ic controlling factor for most coil performance : Now 15 to

20% retention of 77 K, zero field value at 77 K, 1 T ; Goal is first 30% and then 50%• Together with a zero-field Ic of 400 A/4 mm at 77 K, self field 200 A/4 mm at

77 K, 1 T in all field orientations.• Achieve improved performance levels at lower temperatures too (< 65 K)

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0 30 60 90 120 150 180 210 240

Crit

ical

curr

ent (

A/4

mm

)


Standard MOCVD-based HTS tape

MOCVD HTS w/ self-assembled nanostructures

Goal

c-axis

200

10x 77 K, 1 T

0

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1000

0 1 2 3

Crit

ical

cur

rent

(A/c

m-

wid

th)

Thickness (µm)

Goal


Exploring other pathways to improve in-field performance : alternate dopants

• No impact by Ta addition on in-field properties• Double perovskite Ta compounds not formed ?

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0% 5% 10% 15% 20%

Crit

ical

cur

rent

(A/1

2 m

m)

Ta addition

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Crit

ical

cur

rent

(A/1

2 m

m)


0% Ta 7.5% Ta 10% Ta

12.5% Ta 15% Ta 17.5% Ta

1.0 T, 77 K


BYTOGd2O3

Double perovskite, Ba2(Y,RE)TaO6 nanorodsobserved in Ta-doped MOCVD films

Why improvement in in-field performance not seen in Ta-doped MOCVD films even with Ba2(Y,RE)TaO6nanorods ?


Exploring new pathways to improve in-field performance : directed assembly

• In general, in-situ oxide nanostructures based on Zr, Nb, Ta created by self-assembly during HTS film growth have been used to improve in-field performance.

• Epitaxial growth of HTS film simultaneously with self-assembly of nanorods has drawbacks : lack of control of size, distribution, and orientation of nanorods.

• One approach is to direct the nucleation of self-assembled nanorods from pre-deposited nucleation sites on the LMO buffer surface

LMO buffer

Pre-deposited nucleation sites

Pre-deposited nucleation site

BZO nanorod

LMO buffer


Exploring new pathways to improve in-field performance : prefabricated nanorods

• Taking a step further, prefabricated nanorods on buffer surface followed by HTS epitaxial growth can allow for independent control of size, distribution and orientation of nanorods.

• Three techniques developed for prefabricated nanorod growth on LMO on IBAD tapes.


Electrodeposition of silver• Ag in 2G wire is a limiting factor in production capacity and wire cost• Electrodeposition is a lower-cost alternative to vacuum sputtering now used• Can be done in tandem with copper plating further increases production

capacity• Enabler for a low ac loss wire• Silver nitrate in organic solvent• Contact resistivity ~ 4 µΩcm2

• Over current capability with ~ 2 µm electrodeposited Ag = 20% more than Ic : comparablewith sputtered Ag

100 µm

Cu Ag HTS

substrate

Cu

050

100150200250300350400

0 100 200

Volta

ge (µ

v)

Critical Current [A]

Burn out at 207 A, 360 µV

Ic = 171 A


Scaled up electrodeposition of silver• Process scaled up to 100 m

lengths at 60 m/h* even in a small research-scale system

* 4mm wide equivalent

0 20 40 60 80 1000

100

200

300

After Ag Electrodeposition

Critic

al c

urre

nt

(A/1

2 m

m)

Tape Position (m)

0 20 40 60 80 1000

100

200

300

400

Electrodeposition + oxygenation

Critic

al c

urre

nt

(A/1

2 m

m)

Tape Position (m)

0 20 40 60 80 1000

100

200

300

As HTS deposited

Critic

al c

urre

nt

(A/1

2 m

m)

Tape Position (m)

Critical current of HTS wire maintained over 100 m length after electrodepositionof silver & after oxygenation


Transport Ic measurement on 100 m long wire with electrodeposited silver

• Transport Ic of 200 to 250 A/cm measured over 100 m through electrodeposited silver– Silver-HTS interface is good for current transfer– Silver surface is good enough for press electrical contacts

• ED Ag is able to sustain 10 to 20% more current beyond take-off current

-200

20406080

100120

0 50 100 150 200 250 300

Volta

ge (µ

V)

Current (A)

I-V curve measured over 5 m

0

100

200

300

400

0 20 40 60 80 100

Crit

ical

cur

rent

(A/1

2 m

m)

Tape position (m)

Silver electrodeposition is a scalable process for lower wire cost and is an enabler for multifilamentary 2G wire

Transport Ic measured over 5 m


HTS wire R&D is necessary to reach price-performance requirements of commercial market

Commercial market requirements could be reached five to 10 years sooner with R&D.

10

100

1,000

2009 2014 2019 2024

Pric

e ($

/kA

-m)

77 K, 0 T, with R&D77 K, 0 T without R&D65 K, 3 T with R&D65 K, 3 T, without R&D50 K, 3 T with R&D50 K, 3 T, without R&D

commerical market

medium commercialmarket requirementlarge commercialmarket requirement

Several R&D opportunities exist to improve critical current, in-field performance, reduce cost and increase throughput.

Progress in research and development of IBAD-MOCVD based superconducting wires2010... ·...

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Transcript of Progress in research and development of IBAD-MOCVD based superconducting wires2010... ·...