Aluminum alters superconductors

Decisive weaknesses of the superconductor magnesium diboride

Robert j. Cava and his colleagues at princeton university have discovered that the new superconductor (new superconductor magnesium diboride) has critical weaknesses. Jun akimitsu of aoyama-gakuin university in japan and colleagues from other universities had found that magnesium boride could be cooled at the temperature of 39 kelvin (minus 234.15 degrees celsius) has superconducting properties. In the same ie of nature in which they presented their results, robert cava had commented enthusiastically on the groundbreaking discovery: "sensational!". The princeton physicist and superconductor specialist was excited by this simple substance, which can be bought in any chemistry supply store for very little money. It was clear from the start that mgb2 was not a dream material, but experts have repeatedly achieved decisive performance improvements in superconductors in the past, even with minor changes. Cava immediately set to work with his colleagues to test the properties of magnesium boride.

A superconducting ring whose thickness is much coarser than the london penetration depth. The dotted lines symbolize magnetic flux penetration.

In the latest ie of the journal nature, they publish their results, which reveal clear weaknesses of the new material. When electrons are added to mgb2, by partially replacing boron with aluminum, superconductivity is significantly lost. At 10% aluminum, superconductivity decreases decisively, and at 30% al, superconductivity disappears. This means that in magnesium boride there is a clear structural instability associated with the disappearance of superconductivity.

All developments around the new superconductor and the following studies will be the topic of a special session at the upcoming meeting of the american physical society. In nature, indeed, superconducting plastic, organic polymer film (superconducting plastic) was just presented, which is conductive at room temperature and conductive at 2.35 kelvin (minus 270.80 degrees celsius) it becomes superconducting. The international team of researchers from the university of konstanz, lucent technologies (usa) and the institute for solid state physics in zurich discovered "poly (3-hexylthiophene) (p3ht)". The team sees a breakthrough in the use of polymers, as the plastic could be used both as insulation and as a conductive material up to superconductivity, depending on requirements. The decisive factor is the ease and low cost with which these organic polymer materials can be produced. Batlogg of lucent technologies sees the practical use still in the distant future, he referred particularly to the low temperatures, which make so far still an extreme cooling necessary.

Cava, for all his confidence, is of the same opinion: he is convinced that other simple materials, such as magnesium boride, will soon be discovered that have better stability and higher critical temperatures. Nevertheless, he also warns against exaggerated expectations of rapid product maturity of the scientific superconductor findings: "experience shows, however, that the development of practical tools takes a long time. Whether this discovery will prove useful therefore remains to be seen".

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