High Temperature Superconductors (HTS)

With the discovery of the High Temperature Superconductors (HTS) an increasing field of applications extending from energy technique and power application, high frequency electronics to medical technology is escaping. The discovery of HTS itself however was a lucky chance and a sidereal hour in solid state physics and material science.

A long time it seemed that the field of superconductivity tended to saturate. The progress in Tc was minor. The highest superconducting transition temperature Tc of all elemental or alloying materials were found at 23.2 K (Nb3Ge) and the necessary cooling required the expensive liquid Helium. This situation changed suddenly as in the September issue  of the Zeitschrift für Physik in 1986 J.G. Bednorz and K.A. Müller reported about superconductivity at 30 K at a metallic La-Ba-Cu-O compound. The first discovery was soon followed (Jan. 1987) by the investigation of superconductivity at a Y-Ba-Cu-O compound at 92 K in the group of C.W. Chu. The significant progress in enhancing Tc was continued one year later (1988) by the discovery of superconductivity in the Bi-Sr-Ca-Cu-O up to 107 K.

Finally, J.Akimitsu et.al. published in Nature 410 (2001) 63 the discovery of MgB2 with a Tc= 38 K.

From that time a powerful and extensive R&D effort was initiated. Excellent programs and projects around the world had a twofold reason: The basic physical mechanism of superconductivity in the new materials with a copper – oxygen structure was the one target, and the mechanism of Cooper pairing is still not resolved. On the other hand, with the high transition temperature above the boiling temperature of cost - effective liquid Nitrogen (LN2, 77.3 K) the application of the material becomes more probable. To date the highest reliable temperature with Tc = 136 K was found at  HgCaBaCuO material. The “cooling barrier” of superconductors as a long- time standing problem is now significantly lowered stimulating technical developments and applications of this new class of superconducting materials.

After the discovery the investigation of the properties and the HTS materials dominates the first decade. At the end of the 90th of the last century first simple demonstration and functional devices has been developed and tested.

The second and third decade after the HTS discovery was the entrance of HTS products with small market penetration and replacement of conventional technique by HTS technology.  

Within that field Adelwitz Technologiezentrum GmbH (ATZ) is a technology company specialized on in-house R&D, HTS fabrication, construction and assembling of components and devices. In ATZ the HTS system technology (magnet technique, vacuum superinsulation, cryo- technique, and glass / graphite fibre / epoxy composites) is focused on application, such as magnetic bearings and improved electric machines.

HTS history

Fig.:  HTS history