the jc dependence on oxygen doping in polycrystalline forms of bi-2212 with various textures

The Jc Dependence on Oxygen Doping in Polycrystalline Forms of Bi-2212 with

Various Textures

Sept 2002 / 12MC2MC2MC2MC----06060606 ASC’2012, Portland, October 9, 2012ASC’2012, Portland, October 9, 2012ASC’2012, Portland, October 9, 2012ASC’2012, Portland, October 9, 2012 1/22

M O Rikela, A Hobla, J Ehrenberga, J Bocka,S Elschnerb, A Dellicourc, d, e, D Chateignerc,

B Vertruyend, J-F Fagnardd, P.Vanderbemdend

aNexans SuperConductors GmbH, Hürth, GermanybUniversity of Applied Science, Mannheim, Germany

c CRISMAT-ENSICAEN, University of Caen Basse-Normandie, Franced SUPRATECS, University of Liege, Belgium

e Internatinal Doctoral School on Functional Materials

Nexans SuperConductors

Acknowledgments

� D C Larbalestier, F Kametani, J Jiang, A Polyanskii, E. Hellstrom (ASC, NHMFL, Tallahassee)

� H Miao, Y Huang, J Parrell, S Hong (OST, Carteret)

� C. Scheuerlein, A Ballarino, L Bottura (CERN, Geneva).


� S Krämer, J Schramm, C Janke, C Migge, R Deul, Z Abdoulaeva, W Horst, A Klimt, S Hardenberg, J Schütz, D Kobersky, M Gross (NSC, Hürth) M Matras, V Moreau, (ENSCI, Limoges); E. Lugand (EPF, Paris)

� L Lutterotti (University of Trento )

Melt Cast Processed Bulk 2212

Je(77 K; sf) ~ 1 kA/cm2


12 kV/100 & 800 A FCLs

How SuperCurrent flows?

Optimization of Jc(T) in Bi2212 MCP Bulk

What limits SuperCurrent ?


Bicrystal Jc vs Misorientation AngleData for 2212


H. Hilgenkamp and J. Mannhart, Rev. Mod. Phys., Vol. 74, No. 2, 2002, pp. 485-549.

2212 Round Wires and Bulk: High Jcin the absence of Long-Range Texture

2212

Melt Cast Processed


Despite absence of long-range texture powder-in-tube (PIT) Bi-2212 round wire can carry remarkably high Jc values (~105 A/cm2 at 45 T and 4.2 K)

Shen et al, Applied Physics Letters 95, 152516 (2009)].

Jc(66 K = 0.7Tc ) ~ 15 kA/cm2 ~ 20%of best Jc (77 K = 0.7Tc) in Ag/Bi2223

Jc(77 K, 0 T) ~ 5 kA/cm2

Almost no Local Texture

2212

What is Unique in Bi2212 that SuperCurrentFlows across High-Angle GBs ?

� Role of O overdopingShen et al (2009);Rikel et al (2011)

Bulk of the grain

GB

Bulk of the grain

GB


� Special Nature of High-Angle GBsKametani et al 2008, 2010(2MC-07)

Role of O Overdoping

The Jc(77K, sf) dependence on O contents in Bi2Sr2CaCu2O8+δ

� MCP bulk rods and tubes with only slight preferred orientation

� textured Ag sheathed round wires (19x85; 1.2 mm ∅; OST), � textured Ag sheathed tapes


Difference in texture=> Difference in the dominant type of GBs

=> Difference in the optimum overdoping

Jc(77 K, sf) vs Oxygen Contents.Optimum overdoping

90

95

100

1200

1600

2000T

c, K

(77

K, s

f)>,

A/c

m2


75

80

85

0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.240

400

800

T

<Je(

77 K

,

δ in Bi2Sr2CaCu2O8+δ

Tc Data of

Schweizer et al 1993

Tc of MCP-Bulk (21-T-36h )

Jc in 49.2/43 mm dia tube

Jc 8 mm dia rods

Jc 1.2 mm dia RW

Optimum δ0.202 for tube0.204 for 8 mm rod0.212 for OST RW

Rikel et al 2011 (EUCAS)

-3

-2

-1

0

Delta =0.180

Delta = 0.192

Delta = 0.198

Delta = 0.205

log(p

O2 [atm

])

Approach of Glowacki et al (2003) , Yamashita et al (2010)

How we vary O contents?

The δ-pO2-T diagram of Schweizer et al (1993)


-5

-4

3 4 5 6 7 8 9

x = T/100, °Clo

g(p

O2 [

� Anneal at high T for fast equilibration;

� Proof of consistency :

Changes in δ measured for bulk using gravimetry give a good agreement with anticipations

� Cool down along the pO2-T cooling trajectory to suppress O exchange

How we quantify Texture?

F Kametani et al SuST 2011


C Scheuerlein et al 2011

<FWHM> ~ 15°

2 0

4 0

6 0

8 0

1 0 0

1 1

1

1 1

3

1 1

5

1 1

7

2 0

0

2 0

2

20

0,1

Int,

% B i 2 2 1 2 b u l k 1 3 4 - 8 ( 5 ) x = 2 ,0 c h i = 0 ( K a 1 , 8 .6 K )

B i 2 2 1 2 p o w d e r # 4 3 1 1 4 7 3 2 0 1 ( K a 1 2 . 5 K )

B i2 2 1 2 P O = 1 . 7 9 22 0

0

Texture in bulk Bi2212.Approach


2 5 3 0 3 5

0

0 0

8

1 1

1

0 1

7

1 0

8

00

10

2 0

2

00

12

11

9

20

0,1

0 0

9

0 0

11

0 0

13

2 θ , d e g s

)()/()/( 200200 hklRPhklhkl PAAAA ϕ×=

2/32122 )sincos()( −−+= ϕϕϕ POPOP

0

1

2

3

4

5

0 20 40 60 80 100 120 140 160 180

ϕ, °ϕ, °ϕ, °ϕ, °P

( ϕϕ ϕϕ)

Normalized March-Dolase Function

ϕhkl = ϕ = an angle between hkl and 001

FWHM

PO=2.25∫ =180

0

1180/)( ϕϕ dP

Texture in bulk Bi2212.Rough Estimates

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0 1 2 3 4 5 6 7 8

Sample #1

Sample #2

PO00

L

Tube 136-12 (∅ out: 50/in: 35 mm)

PO =1 => isotropic 2212 atouter & inner

surfaces

FWHM ~ 50°


0 1 2 3 4 5 6 7 8Depth, mm

Distance from the surface, mm

)/()(2 22 rRdrrPOrPOR

r

−>=< ∫8 mm rods R45, 3905

FWHM ~ 15-20°

Sample <PO> <FWHM>, °<FWHM>, °<FWHM>, °<FWHM>, °

49/43 mm 1.40(6) 60(5)60(5)60(5)60(5)

8 mm rod 1.71(4) 44(3)44(3)44(3)44(3)

5 mm rod 1.91(8) 37(3)37(3)37(3)37(3)

Samples Studied .Texture Summary

� Bi2212 Bulk (Nexans)

◗ MCP Tubes

OD/ID = 49/43 mm

◗ MCP rods

� 8 and 5 mm diameter

� Fiber Texture

◗ <FWHM> ~ 60°

◗ <FWHM> ~45-35°


� OST Bi2212 Round Wires melt processed at OST for optimizingJe(4.2K, 12 T) = 400 A/mm2

in 1 m long barrel samples

� AzimuthalTexture

◗ <FWHM> ~ 15°

Sample <PO> <FWHM>, °<FWHM>, °<FWHM>, °<FWHM>, ° δδδδ49/43 mm OD/ID 1.40(6) 60(5)60(5)60(5)60(5) 0.2020.2020.2020.202

8 mm rod 1.71(4) 44(3)44(3)44(3)44(3) 0.2040.2040.2040.204

1.2 mm RW 15(2)15(2)15(2)15(2) 0.2120.2120.2120.212

Samples Summary.Cation Composition

� Bi2212 Bulk (Nexans)

◗ MCP Tubes OD/ID = 49/43 mm

◗ MCP rods 8 and 5 mm diameter

� Cation composition

◗ Sr/Ca = 2.35(8)

to reach Tc ~ 94.5 K


� OST Bi2212 Round Wires melt processed at OST for optimizingJe(4.2K, 12 T) = 400 A/mm 2

in 1 m long barrel samples

� Bi2.15Sr1.95Ca0.90Cu2.00O8+δ

◗ Sr/Ca = 2.18(3)

� Bi2.15Sr1.95Ca0.90Cu2.00O8+δ

◗ Sr/Ca = 2.18(3)

� MCP rods 8 mm diameter(precursor lot 79)

Jc vs δδδδin Bi 2Sr2CaCu2O8+δδδδ

with Various Texture with Various Texture and Composition

Refined Jc( δδδδ) for Bulk∆δ0 = 0.013 (8)


δ0 = 0.203(2)

δ0 = 0.190(8)

<FWHM>, °604437


Tc & Ic vs δδδδ in OST RW

∆δ0 = 0.018(8) vs 0.013 (8) in bulk


δ0 = 0.213(4) δδδδ0 = 0.195(7)


Overdoping at 66 K

δ (66 K)= 0.219(3)


δ0 (77K)= 0.213(4)

δ0 (66 K)= 0.219(3)

in agreement with data of Matsumoto et al (2004) on Bi2212 OPIT wire


Ic in Rods and Wire. The same Composition Bi 2.15Sr1.95Ca0.90Cu2.00O8+δδδδ


δ0 = 0.213(4)

δ0 = 0.215(3)


Conclusion

� Overdoping Bi2212 is necessary to optimize Iclower application temperatures need larger overdoping

� The level of overdoping for maximum Jc is within the error independent of the material texture (FWHM from 15 to 60°)


independent of the material texture (FWHM from 15 to 60°)∆δ0 = 0.018(8) in RW vs 0.013(8) in Bi2212 bulkδ0 = 0.213(4) in RW vs 0.215(5) in Bi2212 bulk

� The O contents optimum for Ic is strongly dependent on cation composition:

δ0 = 0.203(2) for Sr/Ca = 2.35(8) δ0 = 0.214(3) for Sr/Ca = 2.18(3)

Practical Consequences

� Optimizing O doping, we improved performance of Bi2212 bulk at 77 K by 20 to 50%Ic(77K,sf) ~ 300 A in 5 mm rods;

600 A in 8 mm rods; 6.3 kA in 49/43 mm (OD/ID) tubes

� Optimization of Bi2212 bulk for applications at lower T should include optimization of cation composition and O


should include optimization of cation composition and O doping Magnetic screens / Trapped-field magnets for 3-5 T at 10-20 K could be possible

� Optimizing O doping should be a part of compositional studies for OPIT round wires:

Thank you

for your attention

OST-Nexans Data 2004-2006

800

1200

1600

2000

Je,

A/m

m2

W521

W522

W523

W524

(b)


0

400

882 884 886 888 890 892 894 896 898 900

T max, °C

Why overall composition of Bi2212 has such a strong effect on performance of round wires and tapes ?

Data of Yamashita et al (2010)

Anticipated, from Bi and Sr ionic radii

measured.MR comment: • Bi contents in 2212 phase should be


Yamashita et al (2010) studied single crystals grown from powders of Bi2+xSr2-xCa1Cu2 cation compositions and annealed to have various O contents. They found that the crystals with smaller Sr/Ca ratio have maximum Tc at stronger overdoping levels. Though the real compositions were not measured, the Sr/Ca ratio in the 2212 phase should scale with that in the overall composition (Rikel et al 2006). Thus, our observation that maximum of Jc(δ) in round wires is at higher δ than in the bulk may stem from the difference in Tc(δ) for bulk (Sr/Ca = 2.45±0.02) and round wire (Sr/Ca = 2.20±0.03). We should first measure Tc of the wires.

• Bi contents in 2212 phase should be almost constant (2.10-2.15)• what is really changed is Sr/Ca ratio. This is reflected in the fall of lattice parameter

Optimum O contens depends on composition

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

Importance for O Uniformity in Bulk

Annealing in air at ~830°C gives uniform O distributionin Bi2Sr2CaCu2O8+δ with δ ~ 0.192

Usual cooling in constant pO2

leads to overdoping of the

surface layer of thickness λ. δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ

δ(x)

λλ


δδδδ ~ 0.20

Tc = 94 Kδδδδ ~ 0.20

Tc = 94 K

Tc(x)Jc0(x)Tc(x)Jc0(x)Tc(x)Jc0(x)Tc(x)Jc0(x)

λλλλλλδδδδ ~ 0.20

Tc = 94 Kδδδδ ~ 0.20

Tc = 94 K


λλλλλλ

c0

Because of the preferred

orientation in MCP bulk,

λ = λab||grad cO ~

100λc| grad cO ~ 1 mm !!

δδδδ ~ 0.20

Tc = 94 Kδδδδ ~ 0.20

Tc = 94 K


λλλλλλδδδδ ~ 0.20

Tc = 94 Kδδδδ ~ 0.20

Tc = 94 K


λλλλλλ

c0

0.1994 K

Improving Performance

Diametermm 21%O2 δδδδ = 0.203

Tube 49/43 900 1420

Cooling

Ic(77 K, sf), A

Jc(77 K, sf), A/cm2

Sample


5 200-250 290-3108 470-520 570-63015 1000 1200

Ic(77 K, sf), A

Rods

Proper Cooling gives 20 to 50% better Perfromance

the jc dependence on oxygen doping in polycrystalline forms of bi-2212 with various textures

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