Superconductors

Development of Superconductors

Materials that have no resistance to the flow of electricity are called superconductors. It is considered to be one of the outer limits of scientific achievement. The limits of superconductivity not yet been reached & theories that explain superconductor behavior seem to be constantly under review. Dutch physicist Heike Kamerlingh Onnes first discovered superconductivity of Mercury in 1911. When he cooled it to the temperature of liquid helium or 4K, its resistance suddenly disappeared. The Kelvin scale is an "absolute" scale of temperature. So, it was necessary for him to come near 4 degrees of the coldest temperature that is theoretically possible to witness superconductivity. Onnes won a Nobel Prize in physics 2 years later for his research in this area.

Year 1933 is when Robert Ochsenfeld & Walter Meissner observed that a superconductor would repel a magnetic field. A magnet moving by a conductor produces currents in the conductor. This is the principle of electric generators. The principle was called diamagnetism. Today, this is known as "Meissner effect". This effect is so strong enough that a magnet can actually be levitated over a superconductor.

In the following decades other superconductors were discovered. In 1941 niobium-nitride was found to superconduct at 16 K. In 1953 vanadium-silicon superconduct at 17.5 K. In 1962 scientists at Westinghouse developed the first commercial superconducting wire, an alloy of niobium and titanium. In the 1960s High-energy, particle-accelerator electromagnets made of copper-clad niobium-titanium were developed at the Rutherford-Appleton Laboratory in the UK, and were first employed in a superconducting accelerator at the Fermilab Tevatron in the US

In 1957 American physicists John Bardeen, Leon Cooper, and John Schrieffer explained the first widely accepted theoretical understanding of superconductivity. Their Theories called BCS Theory of Superconductivity won them a Nobel Prize in 1972. This mathematically complex theory explained superconductivity at temperatures close to absolute zero for elements and simple alloys. At higher temperatures and with different superconductor systems, the BCS theory has become incomplete to explain fully how superconductivity is occurring.

It was in 1962 when Brian D. Josephson, predicted electrical current would flow between 2 superconducting materials even when they are separated by a non-superconductor or insulator. Confirmation of his prediction won him a share of the 1973 Nobel Prize in Physics. This phenomenon is known today as "Josephson effect" and has been applied to electronic devices such as the SQUID, an instrument comparable of detecting even the weakest magnetic fields.

1980 were a decade of unparalleled discovery in the nature of superconductivity. Bill Little of Stanford University had suggested the possibility of organic or carbon-based superconductors in 1964. Danish researcher Klaus Bechgaard of the University of Copenhagen and 3 French team members successfully synthesized the first of these theoretical superconductors in 1980.

In 1986, a remarkable discovery was made in the nature of superconductivity. Alex Müller and Georg Bednorz, researchers at the IBM Research Laboratory in Switzerland, created a brittle ceramic compound that is superconductor at the highest temperature then known, 30 K. Ceramics are normally insulators. They’re not good conductors of electricity. So, researchers had not considered them as potential high-temperature superconductor. The discovery of this first of the superconducting copper-oxides or cuprates won the 2 men a Nobel Prize the following year. Later, it was found that tiny amount of this material were superconducting at 58 K, due to small amount of lead added as a calibration standard.

Müller and Bednorz' observations triggered a flurry of activity in the nature of superconductivity. Researchers began testing ceramics of every imaginable combination in a quest for higher and higher Transition temperature. January of 1987, researchers at the University of Alabama-Huntsville replaced Lanthanum by Yttrium in the Müller and Bednorz molecule and attained an unexpected 92 K Transitional temperature. For the first time a material called YBCO had been found that would superconduct at temperatures warmer than liquid nitrogen. Additional milestones have since been achieved using exotic - and often toxic - elements in the base perovskite ceramic. The world-record transition temperature of 138K is held by a thallium-doped, mercuric-cuprate comprised of the elements Mercury, Thallium, Barium, Calcium, Copper and Oxygen. The transition temperature of this superconductor was confirmed by Dr. Ron Goldfarb at the National Institute of Standards and Technology-Colorado in February of 1994.

ISCO International, once Illinois Superconductor is the first company to capitalize on high-temperature superconductors was formed in 1989. This amalgam of government, private-industry and academic interests introduced a depth sensor for medical equipment that was able to operate at liquid nitrogen temperatures.

Researchers found that at a temperature close to absolute zero an alloy of gold and indium was both a superconductor and a natural magnet in 1997. A material with such properties could not exist according to traditional beliefs! Since then, over a half-dozen such compounds have been found. The discovery of the first high-temperature superconductor that does NOT contain any copper was found in 2000, and the first all-metal perovskite superconductor a year later

Japanese researchers measured the transition temperature of magnesium diboride at 39 Kelvin – way higher than the highest Transition temperature of any of the elemental or binary alloy superconductors also in 2001.

Amazing and almost unbelievable - discoveries like these are forcing scientists to continually re-examine longstanding theories on superconductivity and to consider heretofore-unimagined combinations of elements.