Superconductor classification
 | This article needs to be updated. (November 2015) |
Superconductors
can be classified in accordance with several criteria that depend on physical properties, current understanding, and the expense of cooling them or their material.
By their magnetic properties
- Type I superconductors: those having just one critical field, Hc, and changing abruptly from one state to the other when it is reached.
- upper critical field(Hc2), being in a mixed state when between the critical fields.
- Type-1.5 superconductor – Multicomponent superconductors characterized by two or more coherence lengths
By the understanding we have about them
- Conventional superconductors: those that can be fully explained with the BCS theory or related theories.
- Unconventional superconductors: those that failed to be explained using such theories, e.g.:
This criterion is important, as the BCS theory has explained the properties of conventional superconductors since 1957, yet there have been no satisfactory theories to explain unconventional superconductors fully. In most cases, type I superconductors are conventional, but there are several exceptions such as niobium, which is both conventional and type II.
By their critical temperature
- Low-temperature superconductors, or LTS: those whose critical temperature is below 77 K.
- High-temperature superconductors, or HTS: those whose critical temperature is above 77 K.
- Room-temperature superconductors: those whose critical temperature is above 273 K.
77 K is used as the split to emphasize whether or not superconductivity in the materials can be achieved with liquid nitrogen (whose boiling point is 77K), which is much more feasible than liquid helium (an alternative to achieve the temperatures needed to get low-temperature superconductors).
By material constituents and structure
- Some pure elements, such as lead or mercury (but not all pure elements, as some never reach the superconducting phase).
- Some diamond. [citation needed]
- Some
- Most superconductors made of pure elements are type I (except niobium, silicon, and the above-mentioned Carbon allotropes)
- Most superconductors made of pure elements are type I (except niobium,
- Alloys, such as
- Niobium-titanium(NbTi), whose superconducting properties were discovered in 1962.
- Ceramics (often insulators in the normal state), which include
- Cuprates i.e. copper oxides (often layered, not isotropic)
- The oxides, especially YBa2Cu3O7. They are the most famous high-temperature superconductors
- Nicklates (RNiO2 R=Rare earth ion) where Sr-doped infinite-layer nickelate NdNiO2[1] undergo a superconducting transition at 9-15 K. In the family of Ruddlesden-Popper phase analogon Nd6Ni5O12 (n=5) becomes superconducting at 13 K[2] This is not a complete list and topic of current research.
- Iron-based superconductors, including the oxypnictides
- Magnesium diboride (MgB2), whose critical temperature is 39K,[3] being the conventional superconductor with the highest known temperature.
- non-cuprate oxides such as BKBO
- Cuprates i.e. copper oxides (often layered, not isotropic)
- Palladates – palladium compounds.[4][5]
- other
- e.g. the "metallic" compounds Hg
3NbF
6 and Hg
3TaF
6 are both
See also
- Conventional superconductor
- covalent superconductors
- List of superconductors
- High-temperature superconductivity
- Room temperature superconductor
- Superconductivity
- Technological applications of superconductivity
- Timeline of low-temperature technology
- Type-I superconductor
- Type-II superconductor
- Type-1.5 superconductor
- Heavy fermion superconductor
- Organic superconductor
- Unconventional superconductor
References
- ISSN 1476-4687.
- ISSN 1476-4660.
- S2CID 4388025.)
{{cite journal}}: CS1 maint: multiple names: authors list (link - .
- ^ "Palladium-based compounds may be the superconductors of the future, scientists say".
- .