Class of materials containing oxygen and a group-V element
In chemistry,oxypnictides are a class of materials composed ofoxygen, apnictogen (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. the122 iron arsenides) form a new group ofiron-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 magneticsemiconductors in early 2006.[5]
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]
The firstsuperconducting iron oxypnictide was discovered in 2006, based on phosphorus.[2] A drastic increase in thecritical temperature was achieved when phosphorus was substituted by arsenic.[3] This discovery boosted the search for similar compounds, like the search forcuprate-based superconductors after their discovery in 1986.
The superconductivity of the oxypnictides seems to depend on the iron-pnictogen layers.
^Zimmer, Barbara I.; Jeitschko, Wolfgang; Albering, Jörg H.; Glaum, Robert; Reehuis, Manfred (1995). "The rate earth transition metal phosphide oxides LnFePO, LnRuPO and LnCoPO with ZrCuSiAs type structure".Journal of Alloys and Compounds.229 (2):238–242.doi:10.1016/0925-8388(95)01672-4.
^Shirage, Parasharam M.; Miyazawa, Kiichi; Kito, Hijiri; Eisaki, Hiroshi; Iyo, Akira (2008). "Superconductivity at 43 K at ambient pressure in the iron-based layered compound La1‑xYxFeAsOy".Physical Review B.78 (17) 172503.Bibcode:2008PhRvB..78q2503S.doi:10.1103/PhysRevB.78.172503.
