Oxypnictide

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Class of materials containing oxygen and a group-V element

title: "Oxypnictide" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["superconductors", "pnictides"] description: "Class of materials containing oxygen and a group-V element" topic_path: "general/superconductors" source: "https://en.wikipedia.org/wiki/Oxypnictide" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Class of materials containing oxygen and a group-V element ::

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, interest in these compounds increased dramatically after the publication of the superconducting properties of LaOFeP and LaOFeAs which were discovered in 2006 and 2008. 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.

The different subclasses of oxypnictides are oxynitrides, oxyphosphides, oxyarsenides, oxyantimonides, and oxybismuthides.

Structure

Many of the oxypnictides show a layered structure. For example, LaFePO with layers of La3+O2− and Fe2+P3−.

Superconductivity

The first superconducting iron oxypnictide was discovered in 2006, based on phosphorus. A drastic increase in the critical temperature was achieved when phosphorus was substituted by arsenic. This discovery boosted the search for similar compounds, like the search for cuprate-based superconductors after their discovery in 1986.

The superconductivity of the oxypnictides seems to depend on the iron-pnictogen layers.

Some found in 2008 to be high-temperature superconductors (up to 55 K) of composition ReOTmPn, where Re is a rare earth, Tm is a transition metal and Pn is from group V e.g. As.

::data[format=table title="oxypnictides"]

MaterialTc (K)
LaO0.89F0.11FeAstitle=To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
LaO0.9F0.2FeAsdoi = 10.1209/0295-5075/84/57003
CeFeAsO0.84F0.1641
SmFeAsO0.9F0.143
La0.5Y0.5FeAsO0.643.1
NdFeAsO0.89F0.1152
PrFeAsO0.89F0.1152
GdFeAsO0.8553.5
SmFeAsO~0.8555
::

Tests in magnetic fields up to 45 teslas suggest the upper critical field of LaFeAsO0.89F0.11 may be around 64 T. A different lanthanum-based material tested at 6 K predicts an upper critical field of 122 T in La0.8K0.2FeAsO0.8F0.2.

Practical use

Because of the brittleness of the oxypnictides, superconducting wires are formed using the powder-in-tube process (using iron tubes).

References

References

  1. (1995). "The rate earth transition metal phosphide oxides LnFePO, LnRuPO and LnCoPO with ZrCuSiAs type structure". Journal of Alloys and Compounds.
  2. (2006). "Iron-Based Layered Superconductor: LaOFeP". J. Am. Chem. Soc..
  3. (2008). "Superconductivity at 43 K in an iron-based layered compound LaO1−xFxFeAs". Nature.
  4. Day, Charles. (2008). "New family of quaternary iron-based compounds superconducts at tens of kelvin". Physics Today.
  5. H. Hosono ''et al.'' (2006) [http://www.freepatentsonline.com/EP1868215.html Magnetic semiconductor material] European Patent Application EP1868215
  6. (2008). "Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors". Sci. Technol. Adv. Mater..
  7. (2008). "Synthesis, crystal structure and superconductivity of LaNiPO". Solid State Sciences.
  8. (2008). "Samarium based SmFeAsO1−xFx". Materials Research Innovations.
  9. (2009). "To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report". J. Phys. Soc. Jpn..
  10. Prakash, J.. (2008). "Potassium fluoride doped LaOFeAs multi-band superconductor: Evidence of extremely high upper critical field". EPL.
  11. Shirage, Parasharam M.. (2008). "Superconductivity at 43 K at ambient pressure in the iron-based layered compound La1‑xYxFeAsOy". Physical Review B.
  12. Ren, Z. A.. (2008). "Superconductivity at 52 K in iron based F doped layered quaternary compound Pr[O1–xFx]FeAs". Materials Research Innovations.
  13. Yang, Jie. (2008). "Superconductivity at 53.5 K in GdFeAsO1−δ". Superconductor Science and Technology.
  14. Ren, Zhi-An. (2008). "Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1−δ (Re = rare-earth metal) without fluorine doping". EPL.
  15. (May 29, 2008). "High-temp superconductors pave way for 'supermagnets'". planetanalog.
  16. (2008). "Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields". Nature.
  17. Gao, Zhaoshun. (2008). "Preparation of LaFeAsO0.9F0.1 wires by the powder-in-tube method". Superconductor Science and Technology.

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