2 minute read

Superconductor

Superconductivity Applications

Superconductivity applications fall into two main areas—electromagnets (magnets whose magnetism depends on an externally-powered current passing through a winding) and electronics. In electromagnets, superconducting windings have much lower power consumption than do conventional copper windings, and thus are particularly attractive for high-field applications. Superconducting magnets can be used in magnetic resonance imaging, magnetic sorting of metals, magnetic levitation trains, and magnetic shielding. For power utility applications, superconductors are promising for magnetic energy storage, electrical power transmission, motors, and generators. They are also useful as the coatings for radio-frequency cavities. In electronic applications, thin-film interconnections and Josephson junctions are two key elements. Superconductors offer fast switching speeds and reduced wiring delays so that they are applicable for logic devices and memory cells. Superconducting field-effect transistors and Josephson junction integrated circuits have been demonstrated. At the temperature of liquid nitrogen, 77K, superconductors can be further integrated with semiconductors to form hybrid devices. For sensor operation, superconducting quantum interference devices (SQUIDs), based on the Josephson junction technology, are the most sensitive detector for measuring changes in magnetic field. For example, they can detect they very faint signals (on the order of 10-15 Tesla) produced by the human brain and heart. Also, SQUID-based gradiometry is a very powerful instrument for non-destructive evaluation of nonliving materials. The increased energy gap in HTSCs allows the fabrication of superconducting electromagnetic radiation detectors used for over the spectrum from x ray to the far infrared.

As time goes by, superconductors will find more and more applications. Recently, Y-Ba-Cu-O has been shown to be a good material for the top and bottom electrodes of oxide ferroelectric thin-film capacitors which exhibit fatigue resistance superior to that of capacitors with conventional Pt electrodes (used in dynamic random-access computer memories). This suggests that when the microstructures and the properties of HTSC materials can be well controlled and tailored, oxide superconductors are promising for many hybrid designs—designs incorporating both conventional and superconducting materials. We can also expect upcoming hybrid fabrication technologies. Processes for thin films, thick films, wires, and tapes may all be needed for the integration of a single superconductor-based instrument. Future growth in superconductors technology in electronic components, medical sensing, geology, military technology, transportation, and power transmission and storage is very promising, especially if, as researchers believe, transition temperatures and critical current densities can be significantly increased.

Resources

Books

Bennemann, K.H., J.B. Ketterson, and Joachim A. Kohler, eds. Handbook of Superconductivity. Springer-Verlag, 2003.

Ford, P., and George Saunders. The Rise of Superconductors. Taylor & Francis, 2003.


Periodicals

Orenstein, J., and A.J. Millis. "Advances in the Physics of High-Temperature Superconductivity." Science 280 (April 21, 2000): 468-474.


Pang-Jen Kung

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Critical current density, Jc

—The largest current density that a superconductor can carry nonresistively.

Diamagnetic

—The material with a magnetization vector opposite to the applied magnetic field, which gives rise to a negative magnetic susceptibility.

Josephson junction

—A structure with two superconductors separated by a thin insulating barrier.

Meissner effect

—The expulsion of magnetic flux lines from a superconductor when the superconductor is cooled to a temperature below Tc. Superconducting transition temperature, Tc—The highest temperature at which a given superconducting material remains superconducting.

Thermodynamic critical field, Hc

—Minimum value of externally applied magnetic field that will cause breakdown of diamagnetism in a superconductor.

Additional topics

Science EncyclopediaScience & Philosophy: Stomium to SwiftsSuperconductor - Superconductivity History And Theory, High-temperature Superconductors, Superconductivity Applications