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In chemistry, oxypnictides are a class of materials including 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]


Many of the oxypnictides show a layered structure.[6] For example, LnFePO 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 first superconducting iron oxypnictide was discovered in 2006, based on phosphorus.[2] A drastic increase in the critical temperature was achieved when phosphorus was substituted by arsenic.[3] 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.[8]

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 teslas[15][16] 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.[10]

Practical use[edit]

Because of the brittleness of the oxypnictides, superconducting wires are formed using the powder-in-tube process (using iron tubes).[17]

See also[edit]


  1. ^ Barbara I. Zimmer, Wolfgang Jeitschko, Jörg H. Albering, Robert Glaum and Manfred Reehuis (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. 
  2. ^ a b c Yoichi Kamihara; Hidenori Hiramatsu; Masahiro Hirano; Ryuto Kawamura; Hiroshi Yanagi; Toshio Kamiya & Hideo Hosono (2006). "Iron-Based Layered Superconductor: LaOFeP". J. Am. Chem. Soc. 128 (31): 10012–10013. doi:10.1021/ja063355c. PMID 16881620. 
  3. ^ a b Hiroki Takahashi, Kazumi Igawa, Kazunobu Arii, Yoichi Kamihara, Masahiro Hirano, Hideo Hosono; Igawa; Arii; Kamihara; Hirano; Hosono (2008). "Superconductivity at 43 K in an iron-based layered compound LaO1-xFxFeAs". Nature. 453 (7193): 376–378. Bibcode:2008Natur.453..376T. doi:10.1038/nature06972. PMID 18432191. 
  4. ^ Charles Day (2008). "New family of quaternary iron-based compounds superconducts at tens of kelvin". Physics Today. 61 (5): 11–12. Bibcode:2008PhT....61e..11D. doi:10.1063/1.2930719. 
  5. ^ H. Hosono et al. (2006) Magnetic semiconductor material European Patent Application EP1868215
  6. ^ T C Ozawa and S M Kauzlarich; Kauzlarich (2008). "Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors". Sci. Technol. Adv. Mater. (free-download review). 9 (3): 033003. arXiv:0808.1158free to read. Bibcode:2008STAdM...9c3003O. doi:10.1088/1468-6996/9/3/033003. 
  7. ^ Marcus Tegel, Daniel Bichler and Dirk Johrendt; Bichler; Johrendt (2008). "Synthesis, crystal structure and superconductivity of LaNiPO". Solid State Sciences. 10 (2): 193–197. Bibcode:2008SSSci..10..193T. doi:10.1016/j.solidstatesciences.2007.08.016. 
  8. ^ X. H. Chen, T. Wu, G. Wu, R. H. Liu, H. Chen and D. F. Fang (2008). "Samarium based SmFeAsO1−xFx". Materials Research Innovations. 12 (3): 105. doi:10.1179/143307508X333686. 
  9. ^ a b c d K. Ishida; et al. (2009). "To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report". J. Phys. Soc. Jpn. 78 (6): 062001. arXiv:0906.2045free to read. Bibcode:2009JPSJ...78f2001I. doi:10.1143/JPSJ.78.062001. 
  10. ^ a b Prakash, J.; Singh, S. J.; Samal, S. L.; Patnaik, S.; Ganguli, A. K. (2008). "Potassium fluoride doped LaOFeAs multi-band superconductor: Evidence of extremely high upper critical field". EPL (Europhysics Letters). 84 (5): 57003. Bibcode:2008EL.....8457003P. doi:10.1209/0295-5075/84/57003. 
  11. ^ 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. 
  12. ^ Ren, Z. A.; Yang, J.; Lu, W.; Yi, W.; Che, G. C.; Dong, X. L.; Sun, L. L.; Zhao, Z. X. (2008). "Superconductivity at 52 K in iron based F doped layered quaternary compound Pr[O1–xFx]FeAs". Materials Research Innovations. 12 (3): 105. doi:10.1179/143307508X333686. 
  13. ^ Yang, Jie; Li, Zheng-Cai; Lu, Wei; Yi, Wei; Shen, Xiao-Li; Ren, Zhi-An; Che, Guang-Can; Dong, Xiao-Li; Sun, Li-Ling; et al. (2008). "Superconductivity at 53.5 K in GdFeAsO1−δ". Superconductor Science and Technology. 21 (8): 082001. Bibcode:2008SuScT..21h2001Y. doi:10.1088/0953-2048/21/8/082001. 
  14. ^ Ren, Zhi-An; Che, Guang-Can; Dong, Xiao-Li; Yang, Jie; Lu, Wei; Yi, Wei; Shen, Xiao-Li; Li, Zheng-Cai; Sun, Li-Ling; Zhou, Fang; Zhao, Zhong-Xian (2008). "Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1−δ (Re = rare-earth metal) without fluorine doping". EPL (Europhysics Letters). 83: 17002. arXiv:0804.2582free to read. Bibcode:2008EL.....8317002R. doi:10.1209/0295-5075/83/17002. 
  15. ^ R. Colin Johnson (May 29, 2008). "High-temp superconductors pave way for 'supermagnets'". planetanalog. 
  16. ^ F. Hunte, J. Jaroszynski, A. Gurevich, D. C. Larbalestier, R. Jin, A. S. Sefat, M. A. McGuire, B. C. Sales, D. K. Christen & D. Mandrus; Jaroszynski; Gurevich; Larbalestier; Jin; Sefat; McGuire; Sales; Christen; Mandrus (2008). "Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields". Nature. 453 (7197): 903–905. Bibcode:2008Natur.453..903H. doi:10.1038/nature07058. PMID 18509332. 
  17. ^ Gao, Zhaoshun; Wang, Lei; Qi, Yanpeng; Wang, Dongliang; Zhang, Xianping; Ma, Yanwei (2008). "Preparation of LaFeAsO0.9F0.1 wires by the powder-in-tube method". Superconductor Science and Technology. 21 (10): 105024. Bibcode:2008SuScT..21j5024G. doi:10.1088/0953-2048/21/10/105024. 

Further reading[edit]

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