Oxypnictide
In chemistry, oxypnictides are a class of materials composed of oxygen, a pnictogen (group-V, especially phosphorus and arsenic) and one or more other elements. Although this group of compounds has been recognized since 1995,[1] interest in these compounds increased dramatically after the publication of the superconducting properties of LaOFeP and LaOFeAs which were discovered in 2006[2] and 2008.[3][4] In these experiments the oxide was partly replaced by fluoride.
These and related compounds (e.g. the 122 iron arsenides) form a new group of iron-based superconductors known as iron pnictides or ferropnictides since the oxygen is not essential but the iron seems to be.
Oxypnictides have been patented as magnetic semiconductors in early 2006.[5]
The different subclasses of oxypnictides are oxynitrides, oxyphosphides, oxyarsenides, oxyantimonides, and oxybismuthides.
Structure
Many of the oxypnictides show a layered structure.[6] For example, LaFePO with layers of La3+O2− and Fe2+P3−.[2] This structure is similar to that of ZrCuSiAs, which is now the parent structure for most of the oxypnictide.[7]
Superconductivity
The first
The superconductivity of the oxypnictides seems to depend on the iron-pnictogen layers.
Some found in 2008 to be
Material | Tc (K) |
---|---|
LaO0.89F0.11FeAs | 26[9] |
LaO0.9F0.2FeAs | 28.5[10] |
CeFeAsO0.84F0.16 | 41[9] |
SmFeAsO0.9F0.1 | 43[9] |
La0.5Y0.5FeAsO0.6 | 43.1[11] |
NdFeAsO0.89F0.11 | 52[9] |
PrFeAsO0.89F0.11 | 52[12] |
GdFeAsO0.85 | 53.5[13] |
SmFeAsO~0.85 | 55[14] |
Tests in magnetic fields up to 45
Practical use
Because of the brittleness of the oxypnictides, superconducting wires are formed using the
See also
- Charge-transfer complex – Association of molecules in which a fraction of electronic charge is transferred between them
- Color superconductivity – Predicted phase in quark matter in quarks
- Kondo effect – Physical phenomenon due to impurities
- Magnetic sail – Proposed spacecraft propulsion method
- National Superconducting Cyclotron Laboratory – Building in Michigan, United States
- Spallation Neutron Source – Accelerator-based neutron source in Oak Ridge, Tennessee, USA
- Superconducting radio frequency – Technique used to attain a high quality factor in resonant cavities
- Superfluid film – Thin layer of liquid in a superfluid state
- Timeline of low-temperature technology
References
- .
- ^ PMID 16881620.
- ^ S2CID 498756.
- .
- ^ H. Hosono et al. (2006) Magnetic semiconductor material European Patent Application EP1868215
- PMID 27877997.
- .
- S2CID 55488705.
- ^ S2CID 119295430.
- ^ S2CID 119254951.
- .
- S2CID 55488705.
- S2CID 121990600.
- S2CID 96240327.
- ^ "High-temp superconductors pave way for 'supermagnets'". planetanalog. May 29, 2008.[permanent dead link]
- S2CID 115211939.
- S2CID 122471407.
External links
- Hosono at JST Has diagram of LaO & FeAs layers in LaOFeAs