Advances in High Temperature Superconductors and their applications

Name: Advances in High Temperature Superconductors and their applications
Rating: 5 (1 reviews)

S. MOHAN

Jun 2019 · MJP Publisher

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232

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Prof. Heike Kamerlingh Onnes discovered superconductivity while measuring resistivity of mercury. Surprisingly the resistivity of mercury ceased at 4.2 K and this phenomenon was known as superconductivity. He realized the importance of this discovery in producing large magnetic fieldspl. delateIt was realized that superconductivity is in a new thermodynamic state with peculiar electric and magnetic properties. This paved the way to discover more superconductors. Simple elements such as Tin, Indium or lead showed the highest critical temperature (Tc) 7.2 K. They were called as Type 1 superconductors. Niobium-nitride was found to superconduct at 16 K at 1941 and Vanadium-silicon showed superconductive properties at 17.5 K at 1953. Nb alloys and binary or more complex compounds such as Nb3Sn (Tc – 18 K), Nb-Ti (Tc -9 K), Ga, V with Tc,23 K became type II superconductors. Thereafter, there was not much improvement in the development of superconductor although wonderful applications were expected from superconductors. After three decades, Fullerenes, like ceramic superconductors, are discovered. A decade ago MgB2 was discovered with Tc = 39 K. These superconductors were routinely produced into formof wires for producing larger magnetic fields. In all these cases cooling was effectively done by liquid Helium. A comprehensive microscopic theory of superconductivity in metals was proposed in 1957 by John Bardeen, Leon Cooper and Robert Schrieffer (the so-called “BCS” theory) for which they received the Nobel Prize in Physics. In a major breakthrough, George Bednorz and Karl Mueller discovered a brittle ceramic superconductivity in the family of cuprates at 30 K in 1986 and a new era began. Inspired by the work of Bednorz and Mueller on high temperature superconductivity (HTS), Paul Chu and his associates at the University of Houston discovered in 1987, 123 compounds. That is, YBCO (Yttrium1- Barium2-Copper3- Oxygen7) and iso-structural RBCO (Rare-earth1-Barium2-Copper3-Oxygen7) have a Tc of 93 K. Prior to 1987, all superconducting materials had lower critical temperatures (Tc’s) and therefore functioned only at temperatures near the boiling point of liquid helium (4.2 K) or liquid hydrogen (20.28 K), with the highest being Nb3Ge at 23 K. They were known as low temperature superconductors. YBCO was the first material to become superconducting above 77 K, (boiling point of liquid nitrogen) and subsequently a series of high temperature superconducting materials were discovered. These superconducting materials are widely known as High temperature superconductors as these Tc’s exceeded the limit prescribed by BCS theory. HTSCs are potentially valuable as liquid nitrogen is cheaper than liquid helium. YBCO possesses superior superconducting and physical properties. YBCO receiver coils in NMR-spectrometers have improved the resolution NMR spectrometers by a factor of 3 compared to that achievable with conventional coils. Paul Chu’s group holds the current Tc-record of 164 K in the mercury barium based cuprate superconductor under pressure. Their work led to a rapid succession of new high temperature superconducting materials, ushering in a new era in material science, chemistry and technology. Added to this the structure of Bi2Sr2Ca2Cu2O10(BiSCCO) high temperature superconductive compound having T= 110 K was reported. In 1993, mercuric-cuprates, perovskite ceramic superconductors with the transition temperatures Tc =138 K was also reported.

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About the author

Mohan Sriramulu; B.Sc, M.Sc, Ph.D, D.Sc, Dip. in German, H.R.D, Buss. Management and Administration; Educationist; b April 3, 1947 Chennai, Educ. Madras Univ; Teaching Research Fellow 1969–72; Asst. Prof., Presidency College 1973–80; Reader, Anna University 1980–87; Prof., Pondicherry University 1988–2002, 2005–06; Prof., Asian Inst. Med. Sci. and Tech. (Malaysia) 2003–04; Director–Res. and Dev., PR Inst. of Sci. & Tech. 2006–2007; Vice Chancellor, PRIST University, Thanjavur 2008–2010, Dean, Senior Professor of Materials Science, Hawassa University, Ethiopia 2010– 2012, Dea n-Research, Vel Tech University, 2013,Professor –Emeritus, Vel Tech University, 2017. President: Spectroscopic Soc. of India, Member: Indian Chemical Soc., New York Academy of Sci., Indian Soc. for Experiential Learning, Soc. for Chemists–France, Indian Physics Association, Soc. for the Progress of Sci., International Consortium for Experiential Learning, Laser and Spectroscopic soc. of India, Indian Council for Research in Educational Media; Patron–Spectrophysics Assn. of India, Vice President–Photonics Soc. of India; Publs–More than 800 papers published in various International and National journals of repute and 19 books; Guided 81 Ph.D scholars; organized 10 National conferences, 6 Refresher courses, one Summer school and third International Conf. on Experiential learning at Pondicherry 2002 and International Conf. on Photonics, Nanotechnology and Computer applications 2009. Contributed several papers to Experimental learning; Awards–International Man of the Year 1997, 1998; Best Researcher ISPA award 1999; Scientist of the year 2001 award; Meritorious Educational Excellence award, 2002; Best scientist of the year 2004 award; Best teacher award 2004; Member in the Editorial board of Spectrochim Acta; INCONS 2005 award for Best Teacher, Researcher and Administer, Charles Darwin Gold medal award 2009, Life time achievement award 2014, Address (Res) 7, 3rd cross, Kumaran Nagar Extension, Lawspet, Pondicherry 605 008. (off) Dean, Research, Vel Tech University, Avadi, Chennai 600 062

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