[Saltar al contenido](https://www.sigmaaldrich.com#main-content) [![Merck](https://www.sigmaaldrich.com/static/logos/purple/merck.svg)](https://www.sigmaaldrich.com/ES/es) Productos Carrito0 ESES Productos [Inicio de sesión / Registrarse](https://www.sigmaaldrich.com/oidc-sign-in) [Búsqueda de pedido](https://www.sigmaaldrich.com/ES/es/order-lookup) [Pedido rápido](https://www.sigmaaldrich.com/ES/es/quick-order) Carrito0 [Home](https://www.sigmaaldrich.com/ES/en)[Solid State Synthesis](https://www.sigmaaldrich.com/ES/en/applications/materials-science-and-engineering/solid-state-synthesis)Magnetic Materials: Superconductors # Magnetic Materials: Superconductors ## Superconductors Superconductors are materials which exhibit no electrical resistance below a certain temperature defined as the critical temperature (*TC*). Prior to 1986, the highest *TC* reported was 20 K for Nb3Ge and Nb3Sn.5 In 1986-87, a group lead by Johannes Bednorz and Karl Müller reported the ceramic oxides La2-xBaxCuO4-x and YBa2Cu3O7 (product [328626](https://www.sigmaaldrich.com/ES/en/product/aldrich/328626)) superconduct above the boiling point of nitrogen (77 K).6,7 Materials whose *TC* is greater than the boiling point of nitrogen (a common, readily available, cryogenic coolant) are referred to as high-temperature superconductors (HTS). For their work Bednorz and Müller were awarded the Nobel Prize in Physics in 1987.8 Other more exotic compounds such as fullerides have also exhibited superconducting properties. Fullerides of the formula Ax@C60 (A = K, Rb, Cs) are reported to have superconducting character.9 Although superconductive compounds have been known for nearly a century, the relatively mundane compound magnesium boride has only recently been demonstrated to exhibit superconductivities. Magnesium boride, MgB2 (product [553913](https://www.sigmaaldrich.com/ES/en/product/aldrich/553913)) is not only superconductive but its critical temperature is surprisingly high for a simple ceramic material (Tc = 39 K).10 __Figure 1__ shows an image of a MgB2 wire segment with a tungsten boride core. The wire is formed by reaction of magnesium vapor with a boron filament. The grain structure seen in this image is visible under polarized light.11 __Table 1__ for a comparison of some critical temperatures. ![The cross section of a MgB2](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/materials-science-and-engineering/solid-state-synthesis/superconductors-mag-fig2.gif "superconductors-mag-fig2") __Figure 1.__ The cross section of a MgB2 wire segment. (Image courtesy of D.K. Finnemore, S.L. Bud'ko, P.C. Canfield, Ames Laboratory, Iowa State University.) | | | | | |----------------------|----------|-------------------------------|----------| | Compound or Element | T*C* (K) | Compound or Element | T*C* (K) | | Mercury | 4 | Nb3Sn | 18 | | Vanadium | 5.4 | Nb3Ge | 23 | | Lead | 7.2 | Ba0.6K0.4BiO3 | 30 | | Technetium | 7.8 | Cs2Rb@C60 | 33 | | Niobium | 9.5 | MgB2 | 39 | | Sulfur (at 93 Gpa) | 10 | La1.85Sr0.15CuO4 | 40 | | (CH3CH2)2Cu(NCS)2 | 11.4 | Tl2Ba2CuO6 | 80 | | LiTi2O4 | 12 | YBa2Cu3O7 | 93 | | BaPb0.75Bi0.25O3 | 13 | Tl2Ba2CaCu2O8 | 105 | | YNi2B2C | 15.5 | BiScCO (BiSr2Ca3Cu3O10) | 110 | | NbN | 16 | Tl2Ba2Ca3Cu4O12 | 115 | | V3Ga | 16.5 | Tl2Ba2Ca2Cu3O10 | 125 | | Sulfur (at 160 Gpa)* | 17 | HgBa2Ca2Cu3O10 | 134 | | V3Si | 17 | HgBa2Ca2Cu3O10 (at 30 Gpa)\** | 164 | | Nb3Al | 17.5 | | | Table 1Critical temperatures of some superconductors. \*Highest reported Tc for an element \*\*Highest reported TC to date Superconductivity is governed not only by a critical temperature but also by a critical magnetic field (*HC*) and a critical current density (*JC*). The critical magnetic field refers to an applied magnetic field, such that, if an applied field becomes too large (greater than *HC*) superconductivity will be lost. Critical temperature and critical field are inversely proportional such that just below *TC*, the superconducting state can only be maintained in a very weak applied field, whereas, near 0 K, a larger applied field can be tolerated (__Figure 2__). Similarly, *JC* is the maximum current that can be passed through a superconducting material before it reverts back to a non-superconducting state. This is a critical factor for power applications such as practical superconductor-based electronics would have a *JC* greater than 106 amp·cm-1. ![Effects of temperature and magnetic field on the superconducting state](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/materials-science-and-engineering/solid-state-synthesis/superconductors-mag-fig3.gif "superconductors-mag-fig3") __Figure 2.__Effects of temperature and magnetic field on the superconducting state. Aside from traditional metals based superconductors and HTS cuprate-based ceramics, more recent work has focused upon molecular and fullerene based superconductors. __Related Technical Articles__ - [Role of High Purity Metal Salts in Chemical Synthesis](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/chemistry-and-synthesis/ch-functionalization/role-of-high-purity-metal-salts-in-chemical-synthesis) - [Complex Hydrides: New Solid-state Conductors](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/batteries-supercapacitors-and-fuel-cells/complex-hydrides) - [Mesoporous Oxides and Their Applications to Hydrogen Storage](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/batteries-supercapacitors-and-fuel-cells/mesoporous-oxides) - [Nano Olivine-based Cathode Materials for Li-ion Batteries](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/batteries-supercapacitors-and-fuel-cells/nanostructured-olivine-based-cathode-materials) - [Molecular Monolayers on Silicon Surfaces](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/biosensors-and-imaging/molecular-monolayers) - [Molybdenum Disulfide: Hydrogen Evolution](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/chemical-vapor-deposition/molybdenum-disulfide) - [Innovative Materials for Glass Ionomer Cements (GICs): Dental Applications](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/contact-lens-and-dental-manufacturing/innovative-ionomers-for-dental-applications) - [The Progress in Development of Dental Restorative Materials](https://www.sigmaaldrich.com/ES/en/technical-documents/technical-article/materials-science-and-engineering/contact-lens-and-dental-manufacturing/the-progress-in-development) Arriba __Inicie sesión para continuar.__ Para seguir leyendo, inicie sesión o cree una cuenta. 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