Super conducter


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Superconductors is materials that have no resistance to the flow of electricity below a certain temperature.

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Super conducter

  1. 1. Company Logo
  2. 2. Superconductors is materials thathave no resistance to the flow ofelectricity below a certaintemperature.
  3. 3. As the temperature drops below the critical point, Tc,resistivity rapidly drops to zero and current can flowfreely without any resistance. Thus, superconductorscan carry large amounts of current with little or noloss of energy.
  4. 4. 1) Zero electrical resistivity.This means that an electrical current in asuperconducting ring continuesindefinitely until a force is applied tooppose the current.2) In front of external magnetic fieldit act like diamagnetic material.
  5. 5. In practically Resistivity: s ~ 4x10-23  cm forsuperconductor. Resistivity: m ~ 1x10-13  cm for nonsuperconductor metal (good conductor).
  6. 6. Does it obey the Ohm’s law??? R = V/IIf the voltage is zero, this means that theresistance is zero. Superconductorsare also able to maintain a currentwith no applied voltage whatsoever.
  7. 7. Mechanism inside thesuperconductor In a normal conductor, an electric current maybe visualized as a fluid of electrons movingacross a heavy ionic lattice. The electrons areconstantly colliding with the ions in the lattice,and during each collision some of the energycarried by the current is absorbed by the latticeand converted into heat. As a result, the energycarried by the current is constantly beingdissipated. This is the phenomenon of electricalresistance.The situation is different in a superconductor.
  8. 8. Mechanism inside thesuperconductor In a conventional superconductor, theelectronic fluid cannot be resolved intoindividual electrons. Instead, it consistsof bound pairs of electrons known asCooper pair. This pairing is caused by anattractive force(ΔE) between electronsfrom the exchange of phonons. There is a minimum amount of energyΔE that must be supplied in order toexcite the fluid.
  9. 9. Cont…Therefore,if ΔE > kT( Super fluid)ΔE< kT(not a super fluid)kT= thermal energy of the latticek = Boltzmanns constant (1.38066 x 10-23 J/K)T = temperature of the latticeThe fluid will not be scattered by the lattice.The Cooper pair fluid is thus a superfluid,meaning it can flow without energy dissipation.
  10. 10. Conductor Superconductor
  11. 11. Meissner effectWhen a superconductor is placed in aweak external magnetic field H, andcooled below its transition temperature, it"expels" nearly all magnetic flux and fromits interior; this is called the MeissnereffectThis constraint to zero magnetic field insidea superconductor
  12. 12. Meissner effect
  13. 13. Magnetic Levitation Magnetic fields are actively excludedfrom superconductors (Meissner effect). If a small magnet is brought near asuperconductor, it will be repelledbecause induced super currents willproduce mirror images of each pole. If a small permanent magnet is placedabove a superconductor, it can belevitated by this repulsive force.
  14. 14. Magnetic Levitation
  15. 15. BCS Theory (1957)John Bardeen, Leon Cooper, and John SchreifferThe theory asserts that, as electrons pass through acrystal lattice, the lattice deforms inward towards theelectrons generating sound packets known as"phonons". These phonons produce a trough ofpositive charge in the area of deformation thatassists subsequent electrons in passing through aconductor will attract nearby positive charges in thelattice. This deformation of the lattice causes anotherelectron, with opposite "spin", to move into the regionof higher positive charge density. The two electronsthen become correlated.
  16. 16. BCS Theory
  17. 17. phononsAccording to BCS theory
  18. 18. Types I Superconductors There are pure metals which exhibit zeroresistivity at low temperature. They are called Type I superconductors(Soft Superconductors). The superconductivity exists only belowtheir critical temperature and below acritical magnetic field strength.
  19. 19. Mat. Tc (K)Be 0Rh 0W 0.015Ir 0.1Lu 0.1Hf 0.1Ru 0.5Os 0.7Mo 0.92Zr 0.546Cd 0.56U 0.2Ti 0.39Zn 0.85Ga 1.083Mat. Tc (K)Gd 1.1Al 1.2Pa 1.4Th 1.4Re 1.4Tl 2.39In 3.408Sn 3.722Hg 4.153Ta 4.47V 5.38La 6.00Pb 7.193Tc 7.77Nb 9.46Type ISuperconductors
  20. 20. Types II Superconductors Type 2 category of superconductors becomposed of metallic compounds andalloys They were found to have much highercritical fields and therefore could carrymuch higher current densities whileremaining in the superconducting state.
  21. 21. Type IISuperconductors
  22. 22. High Temperature Superconductor (HTS) Discovered in 1986, HTS ceramics are working at 77K, saving a great deal of cost as compared topreviously known superconductor alloys. However, as has been noted in a Nobel Prizepublication of Bednortz and Muller, these HTSceramics have two technological disadvantages: they are brittle and they degrade under commonenvironmental influences.
  23. 23. HTS Ceramics HTS materials the most popular isorthorhombic YBa2Cu3O7-x (YBCO)ceramics
  24. 24. Some high-Tc superconductorsFormula Tc (K)YBa2Cu3O7 92Bi2Sr2CuO6 20Bi2Sr2CaCu2O8 85Bi2Sr2Ca2Cu3O6 110Tl2Ba2CuO6 80Tl2Ba2CaCu2O8 108Ba2Ca2Cu3O10 125TlBa2Ca3Cu4O11 122HgBa2CuO4 94HgBa2CaCu2O6 128HgBa2Ca2Cu3O8 134
  25. 25. Nobel Prize for Superconductivity 1913 Heike Kamerlingh Onnes on Matter at lowtemperature 1972 John Bardeen, Leon N. Cooper, J. RobertSchrieffer on Theory of superconductivity(BCS) 1973 Leo Esaki, Ivar Giaever, Brian D. Josephsonon Tunneling in superconductors 1987 Georg Bednorz, Alex K. Muller on High-temperature superconductivity 2003 Alexei A. Abrikosov, Vitaly L. Ginzburg,Anthony J. Leggett on Pioneering contributions tothe theory of superconductors and superfluids.
  26. 26. ApplicationMaglev vehicles:Magnetically levitated vehicles are called “maglev”vehicles.The principle of repulsion of magnetic flux can beused in magnetic lavation application
  27. 27. The coaches of the train do not slide oversteel rails, but float on a four inch abovethe track, using superconductingmagnets.Eliminates losses due to friction.400km/hr-500km/hr
  28. 28. APPLICATIONS: Power The cable configuration features aconductor made from HTS wireswound around a flexible hollow core. Ba2Ca2Cu3O10 (BCCO) discovered inJapan. Sumitomo Electric is the worldsfirst company to produce long bismuth-based superconducting wire Liquid nitrogen (77K) flows through thecore, cooling the HTS wire to the zeroresistance state. The conductor is surrounded byconventional dielectric insulation. Theefficiency of this design reduceslosses.
  29. 29. APPLICATIONS: MedicalThe superconducting magnet coils produce a large anduniform magnetic field inside the patients body.MRI (Magnetic Resonance Imaging) scans produce detailedimages of soft tissues.
  30. 30. 1)http://www.superconductors.org2) Wu, J.R. Ashburn, C.J. Torng, P.H. Hor, R.L. Meng, L. Gao,6)Z.J. Huang, Y.Q. Wang and C.W. Chu, Phys. Rev. Letters, 1987. 58, 9087)J. File and R.G. Mills, Phys. Rev. Letters, 1963, 10, 938)J.G. Bednorz and K.A. Muller, Z. Phys., 1986, B64, 1899)J.M. Tarascon, L.H. Greene, W.R. McKinnon, G.W. Hall and10)T.H. Geballe, Science, 1987, 235, 137311)Chemistry in Britain, September 1994 - an issue devoted to the chemistry of 12)superconductingmaterials.13)P.A. Cox, Transition Metal Oxides, Oxford 199214)A.I. Nazzal, V.Y. Lee, E.M. Engler, R.D. Jacowitz, Y. Tokura and15)J.B. Torrance, Physica C, 1988, 153 & 136716)Ivar Giaever - Nobel Lecture. Retrieved 16 Dec 2010.17) BCS Papers:a)L. N. Cooper, "Bound Electron Pairs in a Degenerate Fermi Gas"b)J. Bardeen, L. N. Cooper, and J. R. Schrieffer, "Microscopic Theory of Superconductivity" (1957).c)J. Bardeen, L. N. Cooper, and J. R. Schrieffer, "Theory of Superconductivity"(1957).References
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