
The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite structure ceramic materials discovered by J.G. Bednorz and K.A. Mueller 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 celsius or −459.67 Fahrenheit)), and by other unconventional superconductor 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 °Celsius (77 kelvin). 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 superconductor is ever achieved it will be in a different family of materials. ==See also== *High-temperature superconductivity *Superconductivity Superconductivity
The crystal structure of hi Tc materials are all of the form RR'Cu204, where R and R' are rare earth metals, such as yttrium and barium, or lathnanum and strontium, or barium or strontium. The copper and the oxygen exist two dimensional planes separated by the rare earth metals. The beleif is that it is the copper oxygen planes that are responsible for the superconductivity. The Tc's are of the order or 100 Kelvin at optimal doping. Doping is the removal of electrons from the copper oxygen planes by chemical substitution of the rare earth metals. The "parent compounds" (that is, the stoichiometric compounds before doping) are all magnetically ordered in a state known as "antiferromagnetic", where the electron spins alternate on neighbouring copper atoms. Lanthinum and strontium hi-tc compounds have lower Tc's than yttrium and barium or barium and strontium compouds. ----- Might be nice to have a table with the currently known materials and their Tc's. And maybe a bit about the crystal structure? I'll try to write something if I get a chance. ----- This page should be merged with High-temperature superconductivity User:220.244.224.10 00:36, 16 Mar 2005 (UTC)
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High-temperature superconductor
The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite structure ceramic materials discovered by J.G. Bednorz and K.A. Mueller 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 celsius or −459.67 Fahrenheit)), and by other unconventional superconductor 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 °Celsius (77 kelvin). 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 superconductor is ever achieved it will be in a different family of materials. ==See also== *High-temperature superconductivity *Superconductivity Superconductivity
High-temperature superconductor
The crystal structure of hi Tc materials are all of the form RR'Cu204, where R and R' are rare earth metals, such as yttrium and barium, or lathnanum and strontium, or barium or strontium. The copper and the oxygen exist two dimensional planes separated by the rare earth metals. The beleif is that it is the copper oxygen planes that are responsible for the superconductivity. The Tc's are of the order or 100 Kelvin at optimal doping. Doping is the removal of electrons from the copper oxygen planes by chemical substitution of the rare earth metals. The "parent compounds" (that is, the stoichiometric compounds before doping) are all magnetically ordered in a state known as "antiferromagnetic", where the electron spins alternate on neighbouring copper atoms. Lanthinum and strontium hi-tc compounds have lower Tc's than yttrium and barium or barium and strontium compouds. ----- Might be nice to have a table with the currently known materials and their Tc's. And maybe a bit about the crystal structure? I'll try to write something if I get a chance. ----- This page should be merged with High-temperature superconductivity User:220.244.224.10 00:36, 16 Mar 2005 (UTC)
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