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Spinel group

January 07, 2023

The spinels are any of a class of minerals of general formulation AB
2X
4 which crystallise in the cubic (isometric) crystal system, with the X anions (typically chalcogens, like oxygen and sulfur) arranged in a cubic close-packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice.[1][2] Although the charges of A and B in the prototypical spinel structure are +2 and +3, respectively (A2+
B3+
2X2−
4), other combinations incorporating divalent, trivalent, or tetravalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon, are also possible. The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel.

A and B can also be the same metal with different valences, as is the case with magnetite, Fe3O4 (as Fe2+
Fe3+
2O2−
4), which is the most abundant member of the spinel group.[3] Spinels are grouped in series by the B cation.

The group is named for spinel (MgAl
2O
4), which was once known as "spinel ruby".[4] (Today the term ruby is used only for corundum.)

Spinel group members

Members of the spinel group include:[5]

There are many more compounds with a spinel structure, e.g. the thiospinels and selenospinels, that can be synthesized in the lab or in some cases occur as minerals.

The heterogeneity of spinel group members varies based on composition with ferrous and magnesium based members varying greatly as in solid solution, which requires similarly sized cations. However, ferric and aluminium based spinels are almost entirely homogeneous due to their large size difference.[9]

The spinel structure

 
Crystal structure of spinel

The space group for a spinel group mineral may be Fd3m (the same as for diamond), but in some cases (such as spinel itself, MgAl
2O
4, beyond 452.6 K[10]) it is actually the tetrahedral F43m.[11][12][13]

Normal spinel structures are usually cubic close-packed oxides with eight tetrahedral and four octahedral sites per formula unit. The tetrahedral spaces are smaller than the octahedral spaces. B ions occupy half the octahedral holes, while A ions occupy one-eighth of the tetrahedral holes.[14] The mineral spinel MgAl2O4 has a normal spinel structure.

In a normal spinel structure, the ions are in the following positions (where i, j, and k are arbitrary integers and δ, ε, and ζ are small real numbers): 

X: (1/4-δ, δ, δ ) + ((i+j)/2, (j+k)/2, (i+k)/2) ( δ, 1/4-δ, δ ) + ((i+j)/2, (j+k)/2, (i+k)/2) ( δ, δ, 1/4-δ) + ((i+j)/2, (j+k)/2, (i+k)/2) (1/4-δ, 1/4-δ, 1/4-δ) + ((i+j)/2, (j+k)/2, (i+k)/2) (3/4+ε, 1/2-ε, 1/2-ε) + ((i+j)/2, (j+k)/2, (i+k)/2) (1-ε, 1/4+ε, 1/2-ε) + ((i+j)/2, (j+k)/2, (i+k)/2) (1-ε, 1/2-ε, 1/4+ε) + ((i+j)/2, (j+k)/2, (i+k)/2) (3/4+ε, 1/4+ε, 1/4+ε) + ((i+j)/2, (j+k)/2, (i+k)/2) A: (1/8, 1/8, 1/8) + ((i+j)/2, (j+k)/2, (i+k)/2) (7/8, 3/8, 3/8) + ((i+j)/2, (j+k)/2, (i+k)/2) B: (1/2+ζ, ζ, ζ ) + ((i+j)/2, (j+k)/2, (i+k)/2) (1/2+ζ, 1/4-ζ, 1/4-ζ) + ((i+j)/2, (j+k)/2, (i+k)/2) (3/4-ζ, 1/4-ζ, ζ ) + ((i+j)/2, (j+k)/2, (i+k)/2) (3/4-ζ, ζ, 1/4-ζ) + ((i+j)/2, (j+k)/2, (i+k)/2)

The first four X positions form a tetrahedron around the first A position, and the last four form one around the second A position. When the space group is Fd3m then δ=ε and ζ=0. In this case, a three-fold improper rotation with axis in the 111 direction is centred on the point (0, 0, 0) (where there is no ion) and can also be centred on the B ion at (1/2, 1/2, 1/2), and in fact every B ion is the centre of an improper three-fold rotation. Under this space group the two A positions are equivalent. If the space group is F43m then the improper three-fold rotations become proper three-fold rotations because the inversion disappears, and the two A positions are no longer equivalent.

Every ion is on at least three mirror planes and at least one three-fold rotation axis. The structure has tetrahedral symmetry around each A ion, and the A ions are arranged just like the carbon atoms in diamond.

Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites, while the other half of the B cations occupy tetrahedral sites. An example of an inverse spinel is Fe3O4, if the Fe2+ (A2+) ions are d6 high-spin and the Fe3+ (B3+) ions are d5 high-spin.

In addition, intermediate cases exist where the cation distribution can be described as (A1−xBx)[Ax⁄2B1−x⁄2]2O4, where parentheses () and brackets [] are used to denote tetrahedral and octahedral sites, respectively. The so-called inversion degree, x, adopts values between 0 (normal) and 1 (inverse), and is equal to 2⁄3 for a completely random cation distribution.

The cation distribution in spinel structures are related to the crystal field stabilization energies (CFSE) of the constituent transition metals. Some ions may have a distinct preference for the octahedral site depending on the d-electron count. If the A2+ ions have a strong preference for the octahedral site, they will displace half of the B3+ ions from the octahedral sites to tetrahedral sites. Similarly, if the B3+ ions have a low or zero octahedral site stabilization energy (OSSE), then they will occupy tetrahedral sites, leaving octahedral sites for the A2+ ions.

Burdett and co-workers proposed an alternative treatment of the problem of spinel inversion, using the relative sizes of the s and p atomic orbitals of the two types of atom to determine their site preferences.[15] This is because the dominant stabilizing interaction in the solids is not the crystal field stabilization energy generated by the interaction of the ligands with the d electrons, but the σ-type interactions between the metal cations and the oxide anions. This rationale can explain anomalies in the spinel structures that crystal-field theory cannot, such as the marked preference of Al3+ cations for octahedral sites or of Zn2+ for tetrahedral sites, which crystal field theory would predict neither has a site preference. Only in cases where this size-based approach indicates no preference for one structure over another do crystal field effects make any difference; in effect they are just a small perturbation that can sometimes affect the relative preferences, but which often do not.

Common uses in industry and technology

Spinels commonly form in high temperature processes. Either native oxide scales of metals,[16] or intentional deposition of spinel coatings[17] can be used to protect base metals from oxidation or corrosion. The presence of spinels may hereby serve as thin (few micrometer thick) functional layers, that prevent the diffusion of oxygen (or other atmospheric) ions or specific metal ions such as chromium, which otherwise exhibits a fast diffusion process at high temperatures.

Further reading

  • Biagoni, C.; Pasero, M (2014). "The systematics of the spinel-type minerals: An overview". American Mineralogist. 99 (7): 1254–1264. Bibcode:2014AmMin..99.1254B. doi:10.2138/am.2014.4816. S2CID 102231166.

References

  1. ^ Robert J. Naumann: Introduction to the Physics and Chemistry of Materials CRC Press, 2008, ISBN 978-1-4200-6134-5. Retrieved 15 April 2018.
  2. ^ H-J Meyer: Festkörperchemie in: H-J Meyer (ed.), Riedel Moderne Anorganische Chemie, Walter de Gruyter, 2012, ISBN 978-3-11-024900-2. Retrieved 15 April 2018.
  3. ^ Ernst, W. G. (1969). Earth Materials (Print ed.). Englewood Cliffs, NJ: Prentice-Hall. p. 58.
  4. ^ "ruby spinel". Encyclopædia Britannica. Retrieved 2022-11-25.
  5. ^ Spinel group at Mindat
  6. ^ Rawat, Pankaj Singh; Srivastava, R. C.; Dixit, Gagan; Joshi, G. C.; Asokan, K. (2019). "Facile synthesis and temperature dependent dielectric properties of MnFe2O4 nanoparticles". Dae Solid State Physics Symposium 2018. Vol. 2115. p. 030104. doi:10.1063/1.5112943. S2CID 199183122.
  7. ^ Vestal, Christy R.; Zhang, Z. John (2003). "Effects of Surface Coordination Chemistry on the Magnetic Properties of MnFe2O4 Spinel Ferrite Nanoparticles". Journal of the American Chemical Society. 125 (32): 9828–9833. doi:10.1021/ja035474n. PMID 12904049.
  8. ^ American Elements, Manganese Cobalt Oxide, Spinel Powder.
  9. ^ Ernst, W. G. (1969). Earth Materials (Print ed.). Englewood Cliffs, NJ: Prentice-Hall. p. 59.
  10. ^ Zhang, Liang; Ji, Guang-Fu; Zhao, Feng; Meng, Chuan-Min; Wei, Dong-Qing (February 2011). "The first-principle studies of the crystal phase transitions: Fd3m-MgAl2O4→F4-3m-MgAl2O4". Physica B: Condensed Matter. 406 (3): 335–338. doi:10.1016/j.physb.2010.10.054.
  11. ^ Assadi, M. Hussein N.; H., Katayama-Yoshida (2019). "Covalency a Pathway for Achieving High Magnetisation in TMFe2O4 Compounds" (PDF). J. Phys. Soc. Jpn. 88: 044706. arXiv:2004.10948. doi:10.7566/JPSJ.88.044706. S2CID 127456231.
  12. ^ N. W. Grimes; et al. (Apr 8, 1983). "New Symmetry and Structure for Spinel". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. 386 (1791): 333–345. Bibcode:1983RSPSA.386..333G. doi:10.1098/rspa.1983.0039. JSTOR 2397417. S2CID 96560029.
  13. ^ L. Hwang; et al. (Jul 1973). "On the space group of MgAl
    2    O
    4     spinel". Philosophical Magazine. doi:10.1080/14786437308217448.
  14. ^ Sickafus, Kurt E.; Wills, John M.; Grimes, Norman W. (2004-12-21). "Structure of Spinel". Journal of the American Ceramic Society. 82 (12): 3279–3292. doi:10.1111/j.1151-2916.1999.tb02241.x.
  15. ^ J.K. Burdett, G.L. Price and S.L. Price (1982). "Role of the crystal-field theory in determining the structures of spinels". J. Am. Chem. Soc. 104: 92–95. doi:10.1021/ja00365a019.
  16. ^ Hyun Park, Joo (2007). "Formation Mechanism of Spinel-Type Inclusions in High-Alloyed Stainless Steel Melts". Metallurgical and Materials Transactions B. 38 (4): 657–663. Bibcode:2007MMTB...38..657P. doi:10.1007/s11663-007-9066-x. S2CID 135979316.
  17. ^ Rose, L. (2011). On the degradation of porous stainless steel (Thesis). University of British Columbia. pp. 144–168. doi:10.14288/1.0071732.

January 07, 2023
spinel, group, spinels, class, minerals, general, formulation, which, crystallise, cubic, isometric, crystal, system, with, anions, typically, chalcogens, like, oxygen, sulfur, arranged, cubic, close, packed, lattice, cations, occupying, some, octahedral, tetr. The spinels are any of a class of minerals of general formulation AB2 X4 which crystallise in the cubic isometric crystal system with the X anions typically chalcogens like oxygen and sulfur arranged in a cubic close packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice 1 2 Although the charges of A and B in the prototypical spinel structure are 2 and 3 respectively A2 B3 2 X2 4 other combinations incorporating divalent trivalent or tetravalent cations including magnesium zinc iron manganese aluminium chromium titanium and silicon are also possible The anion is normally oxygen when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel A and B can also be the same metal with different valences as is the case with magnetite Fe3O4 as Fe2 Fe3 2 O2 4 which is the most abundant member of the spinel group 3 Spinels are grouped in series by the B cation The group is named for spinel MgAl2 O4 which was once known as spinel ruby 4 Today the term ruby is used only for corundum Contents 1 Spinel group members 2 The spinel structure 3 Common uses in industry and technology 4 Further reading 5 ReferencesSpinel group members EditMembers of the spinel group include 5 Aluminium spinels Spinel MgAl2O4 after which this class of minerals is named Gahnite ZnAl2O4 Hercynite FeAl2O4 Galaxite MnAl2O4 Pleonaste Mg Fe Al2O4 Iron spinels Cuprospinel CuFe2O4 Franklinite Fe Mn Zn Fe Mn 2O4 Jacobsite MnFe2O4 6 7 Magnesioferrite MgFe2O4 Magnetite FeFe2O4 where one Fe is 2 and two Fe s are 3 respectively Trevorite NiFe2O4 Ulvospinel TiFe2O4 Zinc ferrite Zn Fe Fe2O4 Chromium spinels Chromite FeCr2O4 Magnesiochromite MgCr2O4 Zincochromite ZnCr2O4 Cobalt spinels Manganesecobaltite Mn1 5Co1 5O4 8 Vanadium spinels Coulsonite FeV2O4 Magnesiocoulsonite MgV2O4 Others with the spinel structure Ringwoodite Mg Fe 2SiO4 an abundant olivine polymorph within the Earth s mantle from about 520 to 660 km depth and a rare mineral in meteorites Taaffeite BeMgAl4O8 with an empirical formula as a spinel but the chemical formula is four times as large Musgravite Be Mg Fe Zn 2Al6O12 a type of multi spinel There are many more compounds with a spinel structure e g the thiospinels and selenospinels that can be synthesized in the lab or in some cases occur as minerals The heterogeneity of spinel group members varies based on composition with ferrous and magnesium based members varying greatly as in solid solution which requires similarly sized cations However ferric and aluminium based spinels are almost entirely homogeneous due to their large size difference 9 The spinel structure Edit Crystal structure of spinel The space group for a spinel group mineral may be Fd3 m the same as for diamond but in some cases such as spinel itself MgAl2 O4 beyond 452 6 K 10 it is actually the tetrahedral F4 3m 11 12 13 Normal spinel structures are usually cubic close packed oxides with eight tetrahedral and four octahedral sites per formula unit The tetrahedral spaces are smaller than the octahedral spaces B ions occupy half the octahedral holes while A ions occupy one eighth of the tetrahedral holes 14 The mineral spinel MgAl2O4 has a normal spinel structure In a normal spinel structure the ions are in the following positions where i j and k are arbitrary integers and d e and z are small real numbers X 1 4 d d d i j 2 j k 2 i k 2 d 1 4 d d i j 2 j k 2 i k 2 d d 1 4 d i j 2 j k 2 i k 2 1 4 d 1 4 d 1 4 d i j 2 j k 2 i k 2 3 4 e 1 2 e 1 2 e i j 2 j k 2 i k 2 1 e 1 4 e 1 2 e i j 2 j k 2 i k 2 1 e 1 2 e 1 4 e i j 2 j k 2 i k 2 3 4 e 1 4 e 1 4 e i j 2 j k 2 i k 2 A 1 8 1 8 1 8 i j 2 j k 2 i k 2 7 8 3 8 3 8 i j 2 j k 2 i k 2 B 1 2 z z z i j 2 j k 2 i k 2 1 2 z 1 4 z 1 4 z i j 2 j k 2 i k 2 3 4 z 1 4 z z i j 2 j k 2 i k 2 3 4 z z 1 4 z i j 2 j k 2 i k 2 The first four X positions form a tetrahedron around the first A position and the last four form one around the second A position When the space group is Fd3 m then d e and z 0 In this case a three fold improper rotation with axis in the 111 direction is centred on the point 0 0 0 where there is no ion and can also be centred on the B ion at 1 2 1 2 1 2 and in fact every B ion is the centre of an improper three fold rotation Under this space group the two A positions are equivalent If the space group is F4 3m then the improper three fold rotations become proper three fold rotations because the inversion disappears and the two A positions are no longer equivalent Every ion is on at least three mirror planes and at least one three fold rotation axis The structure has tetrahedral symmetry around each A ion and the A ions are arranged just like the carbon atoms in diamond Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites while the other half of the B cations occupy tetrahedral sites An example of an inverse spinel is Fe3O4 if the Fe2 A2 ions are d6 high spin and the Fe3 B3 ions are d5 high spin In addition intermediate cases exist where the cation distribution can be described as A1 xBx Ax 2B1 x 2 2O4 where parentheses and brackets are used to denote tetrahedral and octahedral sites respectively The so called inversion degree x adopts values between 0 normal and 1 inverse and is equal to 2 3 for a completely random cation distribution The cation distribution in spinel structures are related to the crystal field stabilization energies CFSE of the constituent transition metals Some ions may have a distinct preference for the octahedral site depending on the d electron count If the A2 ions have a strong preference for the octahedral site they will displace half of the B3 ions from the octahedral sites to tetrahedral sites Similarly if the B3 ions have a low or zero octahedral site stabilization energy OSSE then they will occupy tetrahedral sites leaving octahedral sites for the A2 ions Burdett and co workers proposed an alternative treatment of the problem of spinel inversion using the relative sizes of the s and p atomic orbitals of the two types of atom to determine their site preferences 15 This is because the dominant stabilizing interaction in the solids is not the crystal field stabilization energy generated by the interaction of the ligands with the d electrons but the s type interactions between the metal cations and the oxide anions This rationale can explain anomalies in the spinel structures that crystal field theory cannot such as the marked preference of Al3 cations for octahedral sites or of Zn2 for tetrahedral sites which crystal field theory would predict neither has a site preference Only in cases where this size based approach indicates no preference for one structure over another do crystal field effects make any difference in effect they are just a small perturbation that can sometimes affect the relative preferences but which often do not Common uses in industry and technology EditSpinels commonly form in high temperature processes Either native oxide scales of metals 16 or intentional deposition of spinel coatings 17 can be used to protect base metals from oxidation or corrosion The presence of spinels may hereby serve as thin few micrometer thick functional layers that prevent the diffusion of oxygen or other atmospheric ions or specific metal ions such as chromium which otherwise exhibits a fast diffusion process at high temperatures Further reading EditBiagoni C Pasero M 2014 The systematics of the spinel type minerals An overview American Mineralogist 99 7 1254 1264 Bibcode 2014AmMin 99 1254B doi 10 2138 am 2014 4816 S2CID 102231166 References Edit Robert J Naumann Introduction to the Physics and Chemistry of Materials CRC Press 2008 ISBN 978 1 4200 6134 5 Retrieved 15 April 2018 H J Meyer Festkorperchemie in H J Meyer ed Riedel Moderne Anorganische Chemie Walter de Gruyter 2012 ISBN 978 3 11 024900 2 Retrieved 15 April 2018 Ernst W G 1969 Earth Materials Print ed Englewood Cliffs NJ Prentice Hall p 58 ruby spinel Encyclopaedia Britannica Retrieved 2022 11 25 Spinel group at Mindat Rawat Pankaj Singh Srivastava R C Dixit Gagan Joshi G C Asokan K 2019 Facile synthesis and temperature dependent dielectric properties of MnFe2O4 nanoparticles Dae Solid State Physics Symposium 2018 Vol 2115 p 030104 doi 10 1063 1 5112943 S2CID 199183122 Vestal Christy R Zhang Z John 2003 Effects of Surface Coordination Chemistry on the Magnetic Properties of MnFe2O4 Spinel Ferrite Nanoparticles Journal of the American Chemical Society 125 32 9828 9833 doi 10 1021 ja035474n PMID 12904049 American Elements Manganese Cobalt Oxide Spinel Powder Ernst W G 1969 Earth Materials Print ed Englewood Cliffs NJ Prentice Hall p 59 Zhang Liang Ji Guang Fu Zhao Feng Meng Chuan Min Wei Dong Qing February 2011 The first principle studies of the crystal phase transitions Fd3m MgAl2O4 F4 3m MgAl2O4 Physica B Condensed Matter 406 3 335 338 doi 10 1016 j physb 2010 10 054 Assadi M Hussein N H Katayama Yoshida 2019 Covalency a Pathway for Achieving High Magnetisation in TMFe2O4 Compounds PDF J Phys Soc Jpn 88 044706 arXiv 2004 10948 doi 10 7566 JPSJ 88 044706 S2CID 127456231 N W Grimes et al Apr 8 1983 New Symmetry and Structure for Spinel Proceedings of the Royal Society of London Series A Mathematical and Physical Sciences 386 1791 333 345 Bibcode 1983RSPSA 386 333G doi 10 1098 rspa 1983 0039 JSTOR 2397417 S2CID 96560029 L Hwang et al Jul 1973 On the space group of MgAl2 O4 spinel Philosophical Magazine doi 10 1080 14786437308217448 Sickafus Kurt E Wills John M Grimes Norman W 2004 12 21 Structure of Spinel Journal of the American Ceramic Society 82 12 3279 3292 doi 10 1111 j 1151 2916 1999 tb02241 x J K Burdett G L Price and S L Price 1982 Role of the crystal field theory in determining the structures of spinels J Am Chem Soc 104 92 95 doi 10 1021 ja00365a019 Hyun Park Joo 2007 Formation Mechanism of Spinel Type Inclusions in High Alloyed Stainless Steel Melts Metallurgical and Materials Transactions B 38 4 657 663 Bibcode 2007MMTB 38 657P doi 10 1007 s11663 007 9066 x S2CID 135979316 Rose L 2011 On the degradation of porous stainless steel Thesis University of British Columbia pp 144 168 doi 10 14288 1 0071732 Retrieved from https en wikipedia org w index php title Spinel group amp oldid 1123855419, wikipedia, wiki, book, books, library,

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