High-pressure perovskites on the join CaTiO3-FeTiO3

Kurt Leinenweber, J. Linton, A. Navrotsky, Y. Fei, J. B. Parise

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Abstract

An exploratory high-pressure study of the join CaTiO3-FeTiO3 has uncovered two intermediate perovskites with the compositions CaFe3Ti4O12 and CaFeTi2O6. These perovskites have ordering of Ca2+ and Fe2+ on the A sites. Both of these perovskites are unusual in that the A sites containing Fe2+ are either square planar or tetrahedral, due to the particular tilt geometries of the octahedral frameworks. For CaFe3Ti4O12, the structure has been refined from a powder using the Rietveld technique. This compound is a cubic double perovskite (SG Im {Mathematical expression}, a = 7.4672 Å), isostructural with NaMn7O12. Fe2+ is in a square-planar A site (similar to Mn3+ in NaMn7O12) with Fe-O = 2.042(3) Å, with distant second neighbors in a rectangle at Fe-O = 2.780(6) Å. Calcium is in a distorted icosahedron with Ca-O =2.635(5) Å. CaFeTi2O6 crystallizes in a unique tetragonal double perovskite structure (SG P42/nmc, a = 7.5157(2), c = 7.5548(2)), with A-site iron in square-planar (Fe-O = 2.097(2) Å) and tetrahedral (Fe-O = 2.084(2) Å) coordination, again with distant second neighbor oxygens near 2.8 Å. Rietveld refinement was also performed for the previously known perovskite-related form of FeTiO3 recovered from high pressure (lithium niobate type). This compound is trigonal R3c, with a = 5.1233(1) and c = 13.7602(2). The ordered perovskites appear to be stable at 1215 GPa and CaFe3Ti4O12 is found as low as 5 GPa. Thus these perovskites may be important to upper mantle mineralogy, particularly in kimberlites. These compounds are the first known quenchable perovskites with large amounts of A-site ferrous iron, and add greatly to the known occurrences of ferrous iron in perovskites.

Original languageEnglish (US)
Pages (from-to)251-258
Number of pages8
JournalPhysics and Chemistry of Minerals
Volume22
Issue number4
DOIs
StatePublished - Jun 1 1995
Externally publishedYes

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perovskite
Perovskite
Iron
iron
Rietveld refinement
Mineralogy
lithium
tilt
upper mantle
Calcium
mineralogy
Lithium
calcium
Powders
geometry
oxygen
Oxygen
Geometry
Chemical analysis

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

Cite this

High-pressure perovskites on the join CaTiO3-FeTiO3. / Leinenweber, Kurt; Linton, J.; Navrotsky, A.; Fei, Y.; Parise, J. B.

In: Physics and Chemistry of Minerals, Vol. 22, No. 4, 01.06.1995, p. 251-258.

Research output: Contribution to journalArticle

Leinenweber, K, Linton, J, Navrotsky, A, Fei, Y & Parise, JB 1995, 'High-pressure perovskites on the join CaTiO3-FeTiO3', Physics and Chemistry of Minerals, vol. 22, no. 4, pp. 251-258. https://doi.org/10.1007/BF00202258
Leinenweber, Kurt ; Linton, J. ; Navrotsky, A. ; Fei, Y. ; Parise, J. B. / High-pressure perovskites on the join CaTiO3-FeTiO3. In: Physics and Chemistry of Minerals. 1995 ; Vol. 22, No. 4. pp. 251-258.
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abstract = "An exploratory high-pressure study of the join CaTiO3-FeTiO3 has uncovered two intermediate perovskites with the compositions CaFe3Ti4O12 and CaFeTi2O6. These perovskites have ordering of Ca2+ and Fe2+ on the A sites. Both of these perovskites are unusual in that the A sites containing Fe2+ are either square planar or tetrahedral, due to the particular tilt geometries of the octahedral frameworks. For CaFe3Ti4O12, the structure has been refined from a powder using the Rietveld technique. This compound is a cubic double perovskite (SG Im {Mathematical expression}, a = 7.4672 {\AA}), isostructural with NaMn7O12. Fe2+ is in a square-planar A site (similar to Mn3+ in NaMn7O12) with Fe-O = 2.042(3) {\AA}, with distant second neighbors in a rectangle at Fe-O = 2.780(6) {\AA}. Calcium is in a distorted icosahedron with Ca-O =2.635(5) {\AA}. CaFeTi2O6 crystallizes in a unique tetragonal double perovskite structure (SG P42/nmc, a = 7.5157(2), c = 7.5548(2)), with A-site iron in square-planar (Fe-O = 2.097(2) {\AA}) and tetrahedral (Fe-O = 2.084(2) {\AA}) coordination, again with distant second neighbor oxygens near 2.8 {\AA}. Rietveld refinement was also performed for the previously known perovskite-related form of FeTiO3 recovered from high pressure (lithium niobate type). This compound is trigonal R3c, with a = 5.1233(1) and c = 13.7602(2). The ordered perovskites appear to be stable at 1215 GPa and CaFe3Ti4O12 is found as low as 5 GPa. Thus these perovskites may be important to upper mantle mineralogy, particularly in kimberlites. These compounds are the first known quenchable perovskites with large amounts of A-site ferrous iron, and add greatly to the known occurrences of ferrous iron in perovskites.",
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N2 - An exploratory high-pressure study of the join CaTiO3-FeTiO3 has uncovered two intermediate perovskites with the compositions CaFe3Ti4O12 and CaFeTi2O6. These perovskites have ordering of Ca2+ and Fe2+ on the A sites. Both of these perovskites are unusual in that the A sites containing Fe2+ are either square planar or tetrahedral, due to the particular tilt geometries of the octahedral frameworks. For CaFe3Ti4O12, the structure has been refined from a powder using the Rietveld technique. This compound is a cubic double perovskite (SG Im {Mathematical expression}, a = 7.4672 Å), isostructural with NaMn7O12. Fe2+ is in a square-planar A site (similar to Mn3+ in NaMn7O12) with Fe-O = 2.042(3) Å, with distant second neighbors in a rectangle at Fe-O = 2.780(6) Å. Calcium is in a distorted icosahedron with Ca-O =2.635(5) Å. CaFeTi2O6 crystallizes in a unique tetragonal double perovskite structure (SG P42/nmc, a = 7.5157(2), c = 7.5548(2)), with A-site iron in square-planar (Fe-O = 2.097(2) Å) and tetrahedral (Fe-O = 2.084(2) Å) coordination, again with distant second neighbor oxygens near 2.8 Å. Rietveld refinement was also performed for the previously known perovskite-related form of FeTiO3 recovered from high pressure (lithium niobate type). This compound is trigonal R3c, with a = 5.1233(1) and c = 13.7602(2). The ordered perovskites appear to be stable at 1215 GPa and CaFe3Ti4O12 is found as low as 5 GPa. Thus these perovskites may be important to upper mantle mineralogy, particularly in kimberlites. These compounds are the first known quenchable perovskites with large amounts of A-site ferrous iron, and add greatly to the known occurrences of ferrous iron in perovskites.

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