first published Geoff Maile 26JUN1996
Abstract – This paper will provide a brief overview of the discovery and development of superconductivity through this century. From its first baby steps to Nobel status, the ability to transfer electricity though a circuit without loss of energy has long been the holy grail of electrical aspirations. It has been sought because it would herald a new era of technological devices which would not otherwise be possible. And could lead to solving one of the problems of our growing energy needs.
In the year 1911, Heike Kamerling Onnes discovered superconductivity (the ability of a material to carry electricity with no resistance). He cooled mercury to below 4.2 Kelvin by using liquid helium. This enabled an electrical current to pass through his conductor with no loss of energy. It was because of the expense and inconvenience of liquid helium refrigeration, applications of the phenomenon were not considered economically feasible at the time. During the years, it has been found that many metals and alloys can be used in the process. Applications have been developed due to this and the experimentation with higher temperatures that range to 164 degrees Kelvin.. Still to this day the search goes on for a superconductor that functions at room temperature or warmer to supply power to a growing range of new inventions.
In 1932, superconductivity was found in Niobium Carbide (NbC) at 11 Kelvin(K). Next in 1941, Niobium Nitride (NbN) was found to function at 15 K. Next in 1953, a compound with the elements Niobium, Nitrogen and Carbon was found to superconduct at 17 K. 1973 would see the effect in a Niobium and Germanium compound at 23K.
In 1986 researchers at IBM discovered superconductivity in (La-Ba)2CuO4 with a Tc(critical temperature) up to 35 K, in contrast to the previous record of 23 K for which they were awarded the Nobel Prize. By the end of 1986, the observation of superconductivity above 77 K in unusual classes of materials defied the predictions of earlier theories, such as; Bardee-Cooper-Schriffer Theory. These materials are also intriguing because they behave unusually above their Tc’s ; e.g. the Meissner effect. above 77 K were repeatedly observed in relatively impure substances, pushing the belief in the existence of superconductivity in the liquid-nitrogen temperature range. The scientific world knew that theories had to be rewritten after January 1987, when stable and reproducible superconductivity above 90 K was found in the compound Y1Ba2Cu3O7, with Tc close to 100 Kelvin. Superconductivity at such high temperatures defies our common understanding of solids.
Bismuth and thallium superconducting systems were discovered in 1988 which superconduct at 110 K and 125 K, respectively. Under pressure, mercury based compounds were found to function at 164 degrees Kelvin in 1993. Many laboratories throughout the world have reported glimpses of superconductivity at much higher temperatures but these have not yet been confirmed.
To explain the general idea of superconductors, one must look at resistance of electricity. When a solid element is heated the atoms are said to be excited, causing friction. If electricity is conducted through a solid “A”, the electrons will become more exited, raising its temperature. Current is lost through the production of heat Energy caused by friction. To alleviate all friction of the current passing through “A”, “A” must be lowered to a very low temperature, thus calming the atoms of the solid.
In addition to the savings in cost resulting from the change in coolants, liquid helium to liquid nitrogen, it is apparent that superconductivity applications with more inexpensive refrigerants, or eventually no refrigerant at all, may be possible. These new findings are cause for great humility to the previous theorists since the results have changed the way we understand chemical solids. The causes for and consequences of these observations pose a great challenge to chemical scientists to find new compounds for new higher temperature superconductors (HTS) for use in the commercial world. The goal being commercially made long HTS wire that can carry large current without energy loss and can retain excellent superconducting properties over long periods of time without chemical and physical degradation.
Commercial applications of HTS technology in fields such as electric power, transportation, electronics and medicine are now appearing. Present applications of HTS include thin films, wireless communication filters, super fast computer chips, powerful magnets built of superconducting materials for medical magnetic resonance imaging (MRI), high energy accelerators like the proposed Superconducting Supercollider (SSC), very sensitive magnetic field detectors called Superconducting Quantum Interference Devices (SQUIDs), and underground high tension hydro wires.
Future generations are likely to witness significant changes in electricity generation, transmission and storage as well as impacts in microelectronics, communication, computers, and advances in Chemistry. One such application that is planned is a train that hovers and never touches a single track, effectively ridding it of nearly all friction, leaving only wind resistance and gravity due to slight inclines in grade as its inefficiencies.
Another application, one that would revolutionize the way we use energy, is the possibility of making fusion reactor. Powered by this renewable resource, Hydrogen, the most common element, would become cheaply available and could supply our energy needs for the foreseeable future. Hydrogen is efficient and clean to the environment, since there is no waste or by product.
These inventions could not be possible without the superconductor. Thus the discovery of the phenomena of superconductivity will be looked upon as a linchpin in the quest for scientific advancement and for human understanding.
1. H.K. ONNES, LEIDEN COMMUNICATION, (1911)
2. NEW SCIENTIST, P 14, JULY 9TH 1987
3. NEW SCIENTIST, JULY 30TH 1987
4. METALS HANDBOOK, VOL2, 10TH EDIT., SUPERCONDUCTING MATERIALS