Executive Director, Japan Science and Technology Agency (JST)
Harbinger of a high-temperature superconductor boom
—Superconductors make dreams come true—
About 20 years ago, researchers still had not found a metallic superconductor with a critical temperature above 23K. They also had not identified an oxide superconductor with a critical temperature over 11K. In those days, many researchers began to theorize that they would not be able to find new superconductors with high critical temperatures. But in 1986, Prof. Kitazawa read a paper by K. A. Muller and J. G. Bednorz, in which the two IBM researchers pointed out that barium oxides containing divalent copper ions could possibly be superconductors. Like other experts in the field at the time, Prof. Kitazawa had not looked at materials with magnetic ions because the spin magnetic moment of magnetic ions was thought to work against superconductivity.
Prof. Kitazawa thought that barium oxides might become superconductors at low temperature and instructed a senior undergraduate student to study the possibility for his graduation thesis. An oxide prepared by the student showed a Meissner effect at 23K, indicating that the material was superconductive. Almost no experts in this field paid attention to the paper by Muller and Bednorz because they were not superconductivity specialists. However, Prof. Kitazawa led the world’s largest and best team studying oxide superconductors. His team not only showed that the oxide was a superconductor but also found that the material had a layered structure based on copper and oxygen. The announcement of the team’s research results immediately triggered a worldwide superconductor boom. Prof. Kitazawa started searching for new oxide superconductors jointly with his students. At 3 a.m. on the third day of his team’s efforts, he received a phone call at home from one of his students. The student said he had observed unusual signals and asked Prof. Kitazawa to come to the lab immediately. The student was so excited about what he had seen and wanted Prof. Kitazawa to come to the lab right away without waiting for the first train in the morning. Prof. Kitazawa says, “When I arrived at the lab, I saw signals which indicated without a doubt that the material being tested was a superconductor. It was a strontium-based superconductor, and its critical temperature was 40K. Although I did not show the students how excited I was, I think the staff in the laboratory knew because there had been no progress for a long time.”
The study of superconductors usually takes one of two forms: searching for superconductors with higher critical temperatures and studying commercial applications of superconductors with relatively low critical temperatures. Prof. Kitazawa wants to study future commercial applications. Although materials with higher critical temperatures have been found, they currently must be cooled with liquid nitrogen to become superconductors. What commercial applications are worth the cost of cooling superconductors to liquid nitrogen temperatures? Prof. Kitazawa has high expectations for a “Superconducting Global Power Network.”
Through the use of superconducting electric power grids that waste no power during transmission, extra power can be transmitted freely to any place where power is in short supply. This would mean, for example, that problems with solar and wind power generation, which depend heavily on weather conditions and terrain, could be resolved. Prof. Kitazawa says, “If enough people wanted to use an environmentally-friendly renewable energy source that costs twice as much as current sources, then a global power network of superconductors could make it possible. High-temperature superconductors were discovered unexpectedly, but the manufacture of commercial products based on them requires advanced technology. Technological developments in this field are so rapid that the huge number of power transmission cables currently in use could be cut by two to three every month. It won't be long before technology based on superconductivity is applied commercially.” For Prof. Kitazawa, superconductors are tools to be used to create a better future for our children, grandchildren and beyond. He hopes to see these materials contribute to the future of mankind.
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| Fig. 2 Large Image |
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| Superconducting Global Power Network - its basic concept |
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| Fig. 3 Large Image |
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| Advantages of Maglev |
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| Fig. 4 Large Image |
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| Proposed Maglev Paths |
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| Fig.5 Large Image |
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| Three Superconducting Global Networks |
