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Most prominent materials in the high-Tc range are the so-called cuprates, i.e. YBCO (Yttrium-Barium-Copper-Oxide) and related substances.
All known high-Tc superconductors are so-called Type-II superconductors. A Type-II superconductor allows magnetic field to penerate its interior in the units of flux quanta, creating 'holes' (or tubes) of normal metallic regions in the superconducting bulk. This property makes high-Tc superconductors capable of sustaining much higher magnetic fields.
The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Müller in 1986. These materials are characterized by presenting superconductivity at a higher temperature than conventional superconductors (which require temperatures a few degrees above absolute zero (-273.15 °C or -459.67 °F), and by other unconventional features. So-called high-temperature superconductors are generally considered to be those that demonstrate superconductivity at or above the temperature of liquid nitrogen, or -196 °C (77 K).
Recently, other unconventional superconductors have been discovered. Some of them also have unusually high values of the critical temperature Tc, and hence they are sometimes also called high-temperature superconductors, although the record is still held by a cuprate perovskite material (Tc=138 K, that is -135 °C). Nevertheless it is widely believed that if room temperature superconductivity is ever achieved it will be in a different family of materials.
See also
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "High-Temperature Superconductivity"
