Iron(II) selenide

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Iron(II) selenide
Identifiers
CAS number 1310-32-3
PubChem 14795
EC number 215-177-1
Jmol-3D images Image 1
Properties
Molecular formula FeSe
Molar mass 134.81 g/mol
Appearance black crystals
Density 4.72 g/cm3
Melting point 965 °C (1,769 °F; 1,238 K)
Solubility in water 0.975 g/100 mL
Structure
Crystal structure hexagonal
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Iron(II) selenide refers to a number of inorganic compounds of ferrous iron and selenide (Se2-). The phase diagram of the system Fe–Se[1] reveals the existence of several non-stoichiometric phases between ~49 at. % Se and ~53 at. % Fe, and temperatures up to ~450 °C. The low temperature stable phases are the tetragonal PbO-structure (P4/nmm) β-Fe1-xSe and α-Fe7Se8. The high temperature phase is the hexagonal, NiAs structure (P63/mmc) δ-Fe1-xSe. Iron (II) selenide occurs naturally as the NiAs-structure mineral achavalite.

More selenium rich iron selenide phases are the γ phases (γ and γˈ), assigned the Fe3Se4 stoichiometry, and FeSe2, which occurs as the marcasite-structure natural mineral feroselite, or the rare pyrite-structure mineral dzharkenite.

It is used in electrical semiconductors.

Superconductivity[edit]

In 2013 it was reported that a single atomic layer of FeSe epitaxially grown on SrTiO3 is superconductive with a then-record transition temperature for iron-based superconductors of 70K.[2] This discovery has attracted significant attention and in 2014 a superconducting transition temperature of over 100K was reported for this system.[3]

It has been suggested that alternating layers of FeSe and CoSe (cobalt selenide) might boost Tc even further due to proximity effects, cobalt has been used in other pnictogen compounds as a substitute for iron and found to work as well.

References[edit]

  1. ^ Okamoto, H. "The Fe–Se (Iron-Selenium) System." Journal of Phase Equilibria 12, no. 3 (1991): 383–389.
  2. ^ R. Peng et al (2013). "Enhanced superconductivity and evidence for novel pairing in single-layer FeSe on SrTiO3 thin film under large tensile strain". arXiv.  arXiv:1310.3060 [cond-mat.supr-con]
  3. ^ J.-F. Ge et al (2014). "Superconductivity in single-layer films of FeSe with a transition temperature above 100 K". arXiv.  arXiv:1406.3435 [cond-mat.supr-con]