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 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]

oxypnictides
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

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

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See also

References
  1. 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.
  2. Kamihara, Y; Hiramatsu, H; Hirano, M; Kawamura, R; Yanagi, H; Kamiya, T; Hosono, H (2006). "Iron-Based Layered Superconductor: LaOFeP". J. Am. Chem. Soc. 128 (31): 10012–10013. doi:10.1021/ja063355c. PMID 16881620.
  3. Takahashi, H; Igawa, K; Arii, K; Kamihara, Y; Hirano, M; Hosono, H (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. Day, Charles (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. Ozawa, T. C.; Kauzlarich, S. M. (2008). "Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors". Sci. Technol. Adv. Mater. 9 (3): 033003. arXiv:0808.1158. Bibcode:2008STAdM...9c3003O. doi:10.1088/1468-6996/9/3/033003. PMC 5099654. PMID 27877997.
  7. Tegel, Marcus; Bichler, Daniel; Johrendt, Dirk (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. Ren, Z. A.; Yang, J.; Lu, W.; Yi, W.; Che, G. C.; Dong, X. L.; Sun, L. L.; Zhao, Z. X. (2008). "Samarium based SmFeAsO1−xFx". Materials Research Innovations. 12 (3): 105. arXiv:0803.4283. doi:10.1179/143307508X333686.
  9. Ishida, Kenji; Nakai, Yusuke; Hosono, Hideo (2009). "To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report". J. Phys. Soc. Jpn. 78 (6): 062001. arXiv:0906.2045. Bibcode:2009JPSJ...78f2001I. doi:10.1143/JPSJ.78.062001.
  10. 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. 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. arXiv:0803.4283. 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. arXiv:0804.3727. 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. 83: 17002. arXiv:0804.2582. Bibcode:2008EL.....8317002R. doi:10.1209/0295-5075/83/17002.
  15. "High-temp superconductors pave way for 'supermagnets'". planetanalog. May 29, 2008.
  16. Hunte, F; Jaroszynski, J; Gurevich, A; Larbalestier, D. C.; Jin, R; Sefat, A. S.; McGuire, M. A.; Sales, B. C.; Christen, D. K.; Mandrus, D (2008). "Two-band superconductivity in LaFeAsO0.89F0.11 at very high magnetic fields". Nature. 453 (7197): 903–905. arXiv:0804.0485. 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.
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