High-temperature superconductivity

High-temperature superconductivity (high-Tc or HTS) is <a href="/facts/Superconductivity/pqQAlSzJ">superconductivity</a> in materials with a critical temperature (the temperature below which the material behaves as a superconductor) above 77 K (−196.2 °C; −321.1 °F), the boiling point of <a href="/facts/Liquid_nitrogen/IGWI1h00">liquid nitrogen</a>. They are "high-temperature" only relative to previously known superconductors, which function only closer to absolute zero. The first high-temperature superconductor was discovered in 1986 by IBM researchers <a href="/facts/Georg_Bednorz/p14P6Sy6">Georg Bednorz</a> and <a href="/facts/K._Alex_M%25C3%25BCller/89oyE7oM">K. Alex Müller</a>. Although the critical temperature is around 35.1 K (−238.1 °C; −396.5 °F), this material was modified by <a href="/facts/Ching-Wu_Chu/ggU3asoS">Ching-Wu Chu</a> to make the first high-temperature superconductor with critical temperature 93 K (−180.2 °C; −292.3 °F). Bednorz and Müller were awarded the <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a> in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-Tc materials are <a href="/facts/Type-II_superconductor/8V4UTGjY">type-II superconductors</a>.
The major advantage of high-temperature superconductors is that they can be cooled using liquid nitrogen, in contrast to previously known superconductors, which require expensive and hard-to-handle coolants, primarily <a href="/facts/Liquid_helium/JYXCAcDf">liquid helium</a>. A second advantage of high-Tc materials is they retain their superconductivity in higher magnetic fields than previous materials. This is important when constructing <a href="/facts/Superconducting_magnet/bRWH01s5">superconducting magnets</a>, a primary application of high-Tc materials.
The majority of high-temperature superconductors are <a href="/facts/Ceramic/9JKudpqX">ceramics</a>, rather than the previously known metallic materials. Ceramic superconductors are suitable for some practical uses but encounter manufacturing issues. For example, most ceramics are <a href="/facts/Brittle/cn27H2vg">brittle</a>, which complicates wire fabrication. 
The main class of high-temperature superconductors is <a href="/facts/Copper_oxide/zkwqCeLG">copper oxides</a> combined with other metals, especially the <a href="/facts/Rare-earth_barium_copper_oxide/TlqK6YR7">rare-earth barium copper oxides</a> (REBCOs) such as <a href="/facts/Yttrium_barium_copper_oxide/hkFJMegk">yttrium barium copper oxide</a> (YBCO). The second class of high-temperature superconductors in the practical classification is the <a href="/facts/Iron-based_superconductor/SCoUWGmS">iron-based compounds</a>. <a href="/facts/Magnesium_diboride/fsgNsNPP">Magnesium diboride</a> is sometimes included in high-temperature superconductors: It is relatively simple to manufacture, but it superconducts only below 39 K (−234.2 °C), which makes it unsuitable for liquid nitrogen cooling.

High-temperature superconductivity open-in-new

High-temperature superconductivity