temperature dependence of critical currents in rebco ......we fabricated bho doped gdbco films to...
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Coated Conductors for Applications (CCA) 2016, Aspen, Colorado, USA, September 11-14, 2016
Temperature Dependence of Critical Currents in REBCO Coated Conductors
with Artificial Pinning Centers
K. Matsumoto, M. Nishihara, T. Horide, A. K. JhaKyushu Institute of Technology
A. Ichinose, Y. Yoshida, S. Awaji, CRIEPI, Nagoya University, Tohoku Univ.
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✓ Critical Current✓ Anisotropy✓ Grain Boundary✓ Homogeneity✓ AC loss✓ Mechanical property✓ Stability✓ Mass production✓ Costhttp://www.fujikura.co.jp/f‐news/1191427_4018.html
http://www.magnet.fsu.edu/mediacenter/publications/
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Issues in Coated Conductor R & D
✓ Critical Current✓ Anisotropy✓ Grain Boundary✓ Homogeneity✓ AC loss✓ Mechanical property✓ Stability✓ Mass production✓ Cost
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Artificial pinning centers “APCs” -Nanorods
Nanorods
BaZrO3, BaSnO3, Double perovskite, BaHfO3 ,etc
J. MacManus‐Driscoll et al., Nature Mat. 3, 439 (2004)
BaZrO3 column
D. Feldmann et al., SUST 23, 095004 (2010)
Ba2YNbO6 nanorods
Fpmax = 32.3 GN/m3 at 75 K, B//c
H. Tobita et al., SUST 25, 062002 (2012) J. Hanisch et al., SUST 19, 534 (2006)
BaHfO3 nanorods
A. Tsuruta et al., SUST 27, 065001 (2014)
Fpmax = 28.0 GN/m3 at 77.K, B//c
P. Mele et al., SUST 21, 032002 (2008)
BaSnO3 nanorods
Fpmax = 28.3 GN/m3 at 77 K, B//c
C. Varanasi et al., APL 93, 092501 (2008)
✓ Selection of material and
✓ Straightness of nanorods✓ Appropriate diameter of nanorods
✓ Sharp interface
✓ High density without Tc suppression
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Nanoparticles
Artificial pinning centers -Nanoparticles
Y211, Y2O3, BaZrO3, BaSnO3, etc
T. Haugan et al., Nature 430, 867 (2004)
Y211 particles
P. Mele et al., SUST 20, 616 (2007)
Y2O3 particles
Fpmax = 16 GN/m3 at 77 K, B//c
J. Gutierrez et al., Nature Mat. 6, 367 (2007)
BaZrO3 particles
Fpmax = 21 GN/m3 at 77 K, B//c
A. Llordes et al., Nature Mat. 11, 329 (2012)
BaZrO3 particles
Nanoscale strain
M. Miura et al., SUST 26, 035008 (2013)
BaZrO3BaSnO3BaNbO3pure
✓ Selection of material and
✓ Appropriate diameter of nanoparticles
✓ High density without Tc suppression
✓ Sharp interface
✓ Surrounding additional defects
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Variation in APC structures-Hybrid, MLs, segmentation
A. Kiessling et al., SUST 24, 055018 (2011)
MLs
G. Ercolano et al., SUST 24, 095012 (2011)
(Nb‐Ta)YBCO
Fpmax = 26 GN/m3 at 77 K, B//cB. Maiorov et al., Nature Mat. 8, 398 (2009)
Segmentation
T. Horide et al., APL 92, 182511 (2008)
MLs + Segmentation
P. Mele et al., SUST 21, 015019 (2008)
BaZrO3 nanorods Y2O3 particlesBaZrO3 + Y2O3Hybrid APCs
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Formation mechanism and elastic strain studies
J. Slutsker et al., PRB 73, 184127 (2006)
Phase field model
J. MacManus‐Driscoll et al., Nature Mat. 7, 314 (2008)
Epitaxial strain control
J. Wu et al., SUST 27, 044010 (2014)
Modeling of nanorod strain
T. Horide et al., JJAP 53, 083101 (2014)
FEM & first princiiple calcualation
C. Cantoni et al., ACS Nano 5, 4783 (2011)
Strain and oxygen deficiency
A. Llordes et al., Nature Mat. 11, 329 (2012)
Strain evaluation by TEM
S. Wee et al., Adv. Func. Mat. 23, 1912 (2013)
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What should we do next?Nanoscience of flux pinning for coated conductorshas been developing extensively
Development of appropriate pinning centers intocoated conductors for tuning of flux pinningunder the desired temperature and the magneticfield
Appropriate tuning of Jc anisotropy for coildesign
Development of appropriate pinning centers forimprovement of Je
Understanding of flux pinning mechanism ofcoated conductors is very important !
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Recent results of flux pinning R&D
T. Horide et al., APL 108, 082601 (2016)S. Miura et al., APL Mter. 4, 016102 (2016)
Matching field is a key point
> 60 MA/cm2
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Saturation problem of Fp-B curve by nanorod APC
S. Awaji et al., J. Appl. Phys. 111, 013914 (2012)
Fprand :Random pinning force density
Fpcorr :Correlated pinning force density
Fp Fpcorr : B < B
Fp Fprand 2
Fpcorr 2 : B > B
Direct summation, B<BΦ Partial plastic flow, B>BΦ
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Comparison between measured Jc and theoretical limit Jd
02
03 3dJ
λ(T)= λ(0)(1-T/Tc)-1/2
ξ(T)= ξ(0)(1-T/Tc)-1/2
λ(0)=150 nm, ξ(0)=1.5 nm
Jd(4.2 K, 0 T) = 280 MA/cm2
Jd(77 K, 0 T) = 43 MA/cm2
Jc(4.2 K, 0 T) = 60 MA/cm2, Jc/Jd = 21 %Jc(77 K, 0 T) = 8 MA/cm2, Jc/Jd = 18 %
* NbTi wire, Jc/Jd = 5‒10 %
There is still room for the improvement!
B (T) B (T)F
pJ c
Theoretical limit
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Fabrication of BHO nanorods doped GdBCO films
GdBCOBHO
Growth temperature 780ºC
Distance 70 mm
Frequency 1‒10 Hz
pO2 400 mTorr
Substrate LaAlO3 (100)
Pulse number 6000
Energy density 1.5 J/cm2
0vol% 4 vol% 5 vol% 6 vol% 10 vol%
Sample pure 25:1 20:1 39:2 78:4 15:1 20:2 39:4 78:8
GdBCO (pulse) 6000 5770 5714 5707 5707 5625 5456 5442 5442
BHO (pulse) 0 230 286 293 293 375 545 558 558
Thickness (nm) 254 243 150 178 238 243 150 141 165
Alternating target method GdBa2Cu3O7‐x BaHfO3
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Birr curves for BHO doped GdBCO films
T (K)
B irr(T)
20:1
78:4
78:8
39:4
B//c
K. Matsumoto et al., J. Appl. Phys. 116, 163903 (2014)
BΦ≈ 4 TBΦ≈ 5 T
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Jc-B of BHO doped GdBCO films at 65 - 77 K
J c(M
A/cm
2 )θ (deg.)
65 K, 4 T
20:1
25:1
77 K, 2 T
20:1
25:1
pure15:1
pure
15:1
B (T)
J c(M
A/cm
2 )
B//c
20:1
25:1pure15:1
20:1
25:1
pure15:1
65 K
77 K
20:1 shows the highest Jc at 65 & 77 K Jc peak appeared at B//c for 20:1 specimen
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Jc and Fp of BHO doped GdBCO at 10 - 40 K
B (T)
F p(GN/m
3 )
20:1, 10K
25:1, 10K39:2, 10K
pure, 10K
20:1, 20K
25:1, 20K
39:2, 20K
pure, 20K
20:1, 40K
25:1, 40K
39:2, 40Kpure, 40K
B//c
B (T)
J c(M
A/cm
2 )
20:1, 10K
25:1, 10K
39:2, 10K
pure, 10K
20:1, 20K
25:1, 20K
39:2, 20K
pure, 20K
20:1, 40K
25:1, 40K
39:2, 40K
pure, 40K
B//c20
30
2
3
5
7
Jc and Fp of 20:1 is the highest at 10-40 K 1 TN/m3 was observed at 10 K, and more higher value is expected at 4.2 K
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Optimization of ratio of BHO particles to GdBCO
BHO vol. %
F p(GN/m
3 )
F p(GN/m
3 )
F p(GN/m
3 )
BHO vol. %BHO vol. %
B//c, 77 K B//c, 40 K B//c, 10 K
2 T
4 T
6 T
9 T
6 T
3 T
9 T
6 T
Optimized volume fraction of BHO dopant is 5 vol.% within the whole temperature range of 10‒77 K
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Temperature dependence of Jc of BHO-GdBCO
δl pinning : n=5/2δTc pinning : n=7/6
2( ) 1 ( / )n
c cJ T T T Most of specimens show n=2.42‒3.08, ineither cases of B<BΦ and B>BΦ
In both cases, δl pinning is dominantwithin the temperature range of 20-77 K
The range of T<20 K is under studyN. Haberkorn et al., PRB 85, 014522 (2012)
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m = 2.5
m = 1.2
Present, 3T
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Comparison with other group’s data
Maiorov, 0.3T
B. Maioriv et al., nature mater. 8, 398 (2009)
BZO nanorods
Yamasaki, 1T
H. Yamazaki, SUST 29, 065005 (2016)
Y2O3 nanoparticles
MOD BZO
M. Miura, PRB 83, 184519 (2011)
n = 1.24
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How the pinning works in BHO-GdBCO films?
B. Maioriv et al., nature mater. 8, 398 (2009)Tilted Straight
A. Tsuruta et al. : IEEE. Trans. Appl. Supercond. 23, 8001104 (2013)
20 K<T < 60 KKink excitationRandom pins become strongSF, Intrinsic pinning, VacancyDislocation, Twin
60 K<T < 77 K kKink excitationThermal fluctuationRandom pins are weak
0 K < T < 20 KSmall kink excitationRandom pins become strongSF, Intrinsic pinning, VacancyDislocation, Twin
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H/Hc2 = 0.2, = 15°γ= 7, T = 0
Nanorods = 10 % vol.d = 3
Nanoparticles = 2% vol.sd = 3
Can TDGL simulation tell us the better pinning?
= 15°
Magnetic field
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Current
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Jc() of REBCO films with nanorods and hybrid APCs
Jc anisotropy can be tuned by hybrid APC approach
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SummaryWe fabricated BHO doped GdBCO films toinvestigate the temperature dependence of criticalcurrent and flux pinning properties
Matching field BΦ of the specimens are 4‒5 T The GdBCO film of 20:1 ratio (5 vol.%
BHO) has the highest Jc-B characteristicsand Fp = 1 TN/m3 at 10 K
Optimized volume fraction of BHO dopant is5 vol.% within the whole temperature rangeof 10‒77 K
Temperature dependence of BHO dopedGdBCO films show δl pinning behavior