||This article needs to be updated. (November 2015)|
Superconductors can be classified in accordance with several criteria that depend on our interest in their physical properties, on the understanding we have about them, on how expensive is cooling them or on the material they are made of.
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.
- Type II superconductors: having two critical fields, Hc1 and Hc2, being a perfect superconductor under the lower critical field (Hc1) and leaving completely the superconducting state above the upper critical field (Hc2), being in a mixed state when between the critical fields.
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 is explaining the properties of conventional superconductors since 1957, but on the other hand there have been no satisfactory theory to explain fully unconventional superconductors. In most of cases type I superconductors are conventional, but there are several exceptions as niobium, which is both conventional and type II.
By their critical temperature
- Low-temperature superconductors, or LTS: those whose critical temperature is below 30 K.
- High-temperature superconductors, or HTS: those whose critical temperature is above 30 K.
Some now use 77 K as the split to emphasize whether or not we can cool the sample with liquid nitrogen (whose boiling point is 77K), which is much more feasible than liquid helium (the alternative to achieve the temperatures needed to get low-temperature superconductors).
- Some Pure elements, such as lead or mercury (but not all pure elements, as some never reach the superconducting phase).
- Alloys, such as
- Niobium-titanium (NbTi), whose superconducting properties were discovered in 1962.
- Ceramics, which include
- Cuprates i.e. copper oxides
- Iron-based superconductors, including the oxypnictides
- Magnesium diboride (MgB2), whose critical temperature is 39K, being the conventional superconductor with the highest known temperature.
- eg the "metallic" compounds Hg
6 and Hg
6 are both superconductors below 7 K (−266.15 °C; −447.07 °F).
- Conventional superconductor
- covalent superconductors
- List of superconductors
- High-temperature superconductivity
- Room temperature superconductor
- Technological applications of superconductivity
- Timeline of low-temperature technology
- Type-I superconductor
- Type-II superconductor
- Unconventional superconductor
- Jun Nagamatsu, Norimasa Nakagawa, Takahiro Muranaka, Yuji Zenitani and Jun Akimitsu (1 Mar 2001). "Superconductivity at 39 K in magnesium diboride". Nature (letter). 410 (6824): 63–64. Bibcode:2001Natur.410...63N. PMID 11242039. doi:10.1038/35065039.
- W.R. Datars, K.R. Morgan and R.J. Gillespie (1983). "Superconductivity of Hg3NbF6 and Hg3TaF6". Phys. Rev. B 28, 5049-5052. doi:10.1103/PhysRevB.28.5049.