Materials Aspects aud. Application of Superconductivity

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1 Materials Science and Device Technology Materials Aspects and Application of Superconductivity School of Environmental Science and Engineering Toshihiko Maeda, Professor 1

2 Contents apple Self introduction apple Brief introduction to Superconductivity apple Materials Aspects apple Application apple On-going R&D 2

3 Brief introduction to superconductivity 3

4 Electrical Resistance (Resistivity) apple Ohm's law: V=RI V: voltage, I: current, R: resistance R depends on amount of material. apple R=ρL/S ρ: resistivity, L: length, S: cross-section ρ is material constant. apple Joule heat (energy) W=I 2 R S L battery 4

5 Magnetic force lines 5

6 What is superconductivity? apple 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" (T c ). apple T c is very low in our normal sense (its present world record at ambient pressure is 133 K (-140 C)), however, if T c is higher than 77 K (-196 C), we can use cheap liquid nitrogen instead of too expensive liquid helium (4.2 K) for cooling. 6

7 1911: discovered by H. K. Onnes (Leiden Univ., Netherland) apple Resistivity of metals decreases as temperature (T) lowers. apple 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. 7

8 Characterics (on the standpoint of Physics) apple Characteristics of superconductivity is not only "zero resistance" but also zero Joule loss: energy saving apple Perfect Diamagnetism: type I superconductor exclude magnetic flux In type II, this is "imperfect". apple Quantum Vortex apple Josephson Effect 8

9 Type I Superconductor Perfect conductor room-temperature cooling H=0 normal state superconducting state perfect conductor B t = 0 superconductor B t = 0 B = 0 by London 9

10 Superconductor Perfect conductor apple Maxwell's equations D = ρ E = B t B = 0 H = D t + J D=ε 0 E+P=ε r ε 0 E=εE, B=µ 0 H+M=µ r µ 0 H=µH apple We can conclude that "superconducting state" and "normal state" are different phases from each other. 10

11 Why superconductivity: Application apple Zero-resistance very strong electromagnet (NMR, MRI ) energy storage (SMES; superconducting magnetic energy storage) apple Diamagnetism magnetic shielding apple Quantum Vortex highly sensitive magnetic sensor (SQUID etc.) apple Josephson effect highly sensitive magnetic sensor (SQUID etc.) 11

12 3 critical parameters apple Critical temperature (T c ) apple Critical field (H c1, H c2 ) apple Critical current (J c ) the most important parameter for practical application 12

Sn (18.5 K) apple 1960: GL theory apple 1961: Quantum Vortex apple 1961: NbTi (9.

13 Brief History of Superconductivity apple 1908: Liquid Helium apple 1911: discovery of Superconductivity (Hg, Sn, Pb) apple 1933: Meissner effect apple 1935: London equation apple : Type II Superconductor apple 1954: Nb 3 Sn (18.5 K) apple 1960: GL theory apple 1961: Quantum Vortex apple 1961: NbTi (9.8 K) apple 1957: BCS theory apple 1962: Josephson effect apple 1974: Nb 3 Ge (23.2 K) apple 1986: discovery of High-Temperature Superconductivity 13

14 Increasing T c : HTSC 14

15 Materials Aspects 15

16 Element superconductors apple Many elements exhibit superconductivity at 1 atm. Hg, Pb, Sn, Nb, (30 elements) Under high-pressure, much more!) 16

17 Other (Compound) superconductors apple Alloys: NbTi etc. apple Intermetallic compounds: Nb 3 Sn, Nb 3 Al etc. apple Organic compounds: (TMTSF) 2 PF 6 etc. apple Sulfides: PbMo 6 S 8 etc. apple Oxides (Cuprates: high-temperature superconductors) SrTiO 3, Ba(Pb,Bi)O 3 etc. (La,Ba)Cu 2 O 4 YBa 2 Cu 3 O 7 Bi 2 Sr 2 Ca n-1 Cu n O 2n+4, Tl 2 Ba 2 Ca n-1 Cu n O 2n+4 etc. Fe-based Oxides (Arsenides): new comers 17

18 Conventional Superconductors apple At present, superconductors used for practical application are NbTi (bcc) and Nb 3 Ti only. Nb 3 Sn: A15 structure 18

19 YBa 2 Cu 3 O z apple The first material having T c higher than 77 K (T c 90 K for z 7; quite sensitive on z value). apple The structure is oxygen-deficient triple perovskite. 19

20 Perovskite structure apple Ionic crystal with chemical formula of ABO 3. apple Many functional oxides with 3d transition metals. apple The most famous one is (probably) BaTiO 3 in which TiO 6 octahedron is slightly distorted. 20

21 Examples of Application 21

22 Labo. application High-field magnet SQUID NMR 22

23 Medical application (MRI) apple Magnetic Resonance Inspection 23

24 Transportation (MAGLEV) apple Magnetically Levitation Train Apr. 21, 2015: World record: 603 km/h 24

25 Large scale application apple LHC: Large hadron collider (CERN) Nobel prize in 2013 Japanese suppliers contribute a lot. 25

26 On going R&D apple Superconducting power cable 1 st generation wire: Ag-sheathed Bi 2 Sr 2 Ca 2 Cu 3 O 10 : powder sintering 26

27 2 nd generation wire (epitaxial thin film) 27

28 PLD apparatus 28

29 XRD profile of YBCO film 6 PLD-YBCO/(100) NiO single crystal (005) NiO (200) (006) CuKα Intensity / 10 4 cps T 4 sub =680 C 2 0 (001) (002) (003) (004) (007) (008) (009) θ/degree 29

30 Pole figure NiO <100> 0 α=0 β NiO <010> 90 YBCO (102) CuKα 2θ=27.56 α: 15~90 β: 0~360 α α=

31 β-scan profile 1200 PLD-YBCO/NiO(100) single crystal CuKα Intensity / cps YBCO (102) 2θ=27.56 α=34 FWHM= β/degree 31

32 Temperature dependence of resistivity Resistivity, ρ/(µω cm) PLD-YBCO/(100) NiO single crystal I=0.01 ma Temperature, T/K 32

33 I-V characterics at PLD-YBCO/(100) NiO single crystal Voltage, V/µV Temperature: 77.3 K thickness: 180 nm width: 173 µm length: 0.69 mm I c =1.05 A corresponding to: I c *= 60.7 A for 10 mm width J c = 3.3 MA/cm 2 1 µv Current, I/A 33

$fractured surface for PLD-YBCO/NiO$ structure 1 µm 200 nm YBCO YBCO

34 Cross sectional HRSEM images of fractured surface for PLD-YBCO/NiO structure 1 µm 200 nm YBCO YBCO 180 nm NiO NiO (taken by Kyoto Univ.) 34

35 TEM image of interface structure of PLD-YBCO/(100) NiO single crystal YBCO NiO 100 nm 35

36 Summary apple Superconductivity hopeful interesting cute 36

37 That's all!! Thank you for your attention!! Submit your report at the beginning of next lecture. 37

Superconductivity Ref: Richerson, Dekker, 2nd Ed., 1992, pp

MME 467: Ceramics for Advanced Applications Lecture 23 Superconductivity Ref: Richerson, Dekker, 2nd Ed., 1992, pp.239 248. Prof. A. K. M. B. Rashid Department of MME, BUET, Dhaka Topics to discuss...!