Materials Aspects and Application of SuperconductivityJuly 9, 2015 Materials Aspects aud Applications Superconductivity 1 Materials Aspects and Application of Superconductivity July

July 9, 2015 Materials Aspects aud Applications Superconductivity

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Materials Aspects and

Application of Superconductivity July 9, 2015

School of Environmental Science and Engineering

Toshihiko Maeda, Professor

Materials Science and Device Technology


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Contents

 Self introduction

 Brief introduction to Superconductivity

 Materials Aspects

 Application

 On-going R&D

Brief introduction to superconductivity


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Electrical Resistance (Resistivity)

 Ohm's law: V=RI ♠ V: voltage, I: current, R: resistance ♠ R depends on amount of material.

 R=ρL/S ♠ ρ: resistivity, L: length, S: cross-section ♠ ρ is material constant.

 Joule heat (energy) ♠ W=I2R


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battery

S

L

Magnetic force lines


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What is superconductivity?

 In some materials, electrical resistance is absolutely zero below a certain temperature. This phenomenon is called "superconductivity" and this characteristic temperature is called "critical temperature" or "superconductivity transition temperature" (Tc).

 Tc is very low in our normal sense (its present world record at ambient pressure is 133 K (-140˚C)), however, if Tc is higher than 77 K (-196˚C), we can use cheap liquid nitrogen instead of too expensive liquid helium (4.2 K) for cooling. July 9, 2015 Materials Aspects aud

Applications Superconductivity 6

1911: discovered by H. K. Onnes (Leiden Univ., Netherland)

 Resistivity of metals ♠ decreases as temperature (T) lowers.

 At absolute zero (0 K, -273˚C), does it go down to zero or diverge to infinity? ♠ Using highly pure metal (mercury; Hg) and

liquid helium (liq. He), Onnes measured temperature-dependence of resistivity, and then, discovered "Superconductivity".

♠ Hg is liquid at room-temperature, so Hg is easily vaporized. By re-condensation, highly pure Hg can be obtained.


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Characterics (on the standpoint of Physics)  Characteristics of superconductivity is not only

"zero resistance" but also •••♠ zero Joule loss: energy saving

 Perfect Diamagnetism: type I superconductor♠ exclude magnetic flux♠ In type II, this is "imperfect".

 Quantum Vortex Josephson Effect


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Type I Superconductor ≠ Perfect conductor


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cooling

room-temperature

H=0

perfect conductor

superconductor

B = 0normal state superconducting state by London

∂B∂t

= 0

∂B∂t

= 0

Superconductor ≠ Perfect conductor

 Maxwell's equations

♠  D=ε0E+P=εrε0E=εE, B=µ0H+M=µrµ0H=µH

 We can conclude that "superconducting state" and "normal state" are different phases from each other. July 9, 2015 Materials Aspects aud

Applications Superconductivity 10

€

∇ • D = ρ

∇ × E = −∂B∂t

∇ • B = 0

∇ × H = −∂D∂t

+ J

Why superconductivity: Application

 Zero-resistance♠ very strong electromagnet (NMR, MRI ••••)♠ energy storage (SMES; superconducting magnetic energy storage)

 Diamagnetism♠ magnetic shielding

 Quantum Vortex ♠ highly sensitive magnetic sensor (SQUID etc.)

 Josephson effect♠ highly sensitive magnetic sensor (SQUID etc.)


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3 critical parameters

 Critical temperature (Tc)

 Critical field (Hc1, Hc2)

 Critical current (Jc) ♠ the most important parameter for

practical application


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Brief History of Superconductivity

  1908: Liquid Helium  1911: discovery of Superconductivity (Hg, Sn, Pb)  1933: Meissner effect  1935: London equation  1935-37: Type II Superconductor  1954: Nb3Sn (18.5 K)  1960: GL theory  1961: Quantum Vortex   1961: NbTi (9.8 K)  1957: BCS theory  1962: Josephson effect  1974: Nb3Ge (23.2 K)  1986: discovery of High-Temperature Superconductivity


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Increasing Tc: HTSC

Materials Aspects


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Element superconductors

 Many elements exhibit superconductivity at 1 atm. ♠ Hg, Pb, Sn, Nb, ••• (30 elements) ♠ Under high-pressure, much more!)


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Other (Compound) superconductors

 Alloys: NbTi etc.  Intermetallic compounds: Nb3Sn, Nb3Al etc.  Organic compounds: (TMTSF)2PF6 etc.  Sulfides: PbMo6S8 etc.  Oxides (Cuprates: high-temperature superconductors)

♠ SrTiO3, Ba(Pb,Bi)O3 etc. ♠ (La,Ba)Cu2O4

♠ YBa2Cu3O7 ♠ Bi2Sr2Can-1CunO2n+4, Tl2Ba2Can-1CunO2n+4 etc. ♠ Fe-based Oxides (Arsenides): new comers


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Conventional Superconductors

 At present, superconductors used for practical application are NbTi (bcc) and Nb3Ti only.


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Nb3Sn: A15 structure

YBa2Cu3Oz

 The first material having Tc higher than 77 K (Tc≈90 K for z≈7; quite sensitive on z value).

 The structure is oxygen-deficient triple perovskite.


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Perovskite structure


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 Ionic crystal with chemical formula of ABO3.  Many functional oxides with 3d transition metals.  The most famous one is (probably) BaTiO3 in

which TiO6 octahedron is slightly distorted.

Examples of Application


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Labo. application


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High-field magnet SQUID NMR

Medical application (MRI)

 Magnetic Resonance Inspection


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Transportation (MAGLEV)

 Magnetically Levitation Train


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Apr. 21, 2015: World record: 603 km/h

Large scale application

 LHC: Large hadron collider (CERN)♠ Nobel prize in 2013♠ Japanese suppliers contribute a lot.


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On going R&D

 Superconducting power cable


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1st generation wire: Ag-sheathed Bi2Sr2Ca2Cu3O10: powder sintering

2nd generation wire (epitaxial thin film)


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PLD apparatus

July 9, 2015 28Materials Aspects aud Applications Superconductivity

July 9, 2015 29

0

2

4

6

0 10 20 30 40 50 60 70 80

Inte

nsity

/ 10

4 cps

2θ/degree

CuKα

NiO

(200

)

(001

) (002

)

(003

)

(004

)

(005

) (006

)

(007

)

(008

)

(009

)

PLD-YBCO/(100) NiO single crystal

XRD profile of YBCO film

Tsub=680˚C

Materials Aspects aud Applications Superconductivity

July 9, 2015 30

Pole figure

α

β

0˚

90˚

180˚

270˚α=90˚

α=0˚

YBCO (102)

NiO <100>

NiO <010>

CuKα2θ=27.56˚α: 15~90˚β: 0~360˚


July 9, 2015 31

0

200

400

600

800

1000

1200

0 90 180 270 360β/degree

Inte

nsity

/ cp

s

CuKαPLD-YBCO/NiO(100) single crystal

YBCO (102)・2θ=27.56˚・α=34˚

FWHM=1.9˚

β-scan profile


July 9, 2015 32

Temperature dependence of resistivity

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Resi

stiv

ity, ρ

/(µΩ

•cm

)

Temperature, T/K

I=0.01 mA

0

20

40

60

80

100

88 90 92



July 9, 2015 33

I-V characterics at 77 Ｋ

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Volta

ge, V

/µV

Current, I/A


1 µVcorresponding to: ♦ Ic*= 60.7 A for 10 mm width ♦ Jc = 3.3 MA/cm2

Temperature: 77.3 Kthickness: 180 nmwidth: 173 µmlength: 0.69 mm

Ic=1.05 A


July 9, 2015 34

Cross sectional HRSEM images of fractured surface for PLD-YBCO/NiO structure

180 nmYBCOYBCO

NiONiO

YBCOYBCO

NiONiO

200 nm1 µm

(taken by Kyoto Univ.)


July 9, 2015 35

TEM image of interface structure ofPLD-YBCO/(100) NiO single crystal

100 nm

YBCO

NiO


Summary

 Superconductivity

♠ hopeful

♠ interesting

♠ cute


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That's all !!

Thank you for your attention !!

Submit your report at the beginning of next lecture.


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Documents

Materials Aspects and Application of SuperconductivityJuly 9, 2015 Materials Aspects aud Applications Superconductivity 1 Materials Aspects and Application of Superconductivity July