Perovskite

Perovskite (pronunciation: /pəˈrɒvskaɪt/) is a calcium titanium oxide mineral composed of calcium titanate (CaTiO3). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO3 (XIIA2+VIB4+X2−3), known as the perovskite structure.[5] Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.[6]

This article is about the mineral. For synthetic compounds, see Perovskite (structure).
Perovskite
Crystals of perovskite on matrix
General
CategoryOxide minerals
Formula
(repeating unit)		CaTiO3
Strunz classification4.CC.30
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Identification
Formula mass135.96 g/mol
ColorBlack, reddish brown, pale yellow, yellowish orange
Crystal habitPseudo cubic – crystals show a cubic outline
Twinningcomplex penetration twins
Cleavage[100] good, [010] good, [001] good
FractureConchoidal
Mohs scale hardness5–5.5
LusterAdamantine to metallic; may be dull
Streakgrayish white
DiaphaneityTransparent to opaque
Specific gravity3.98–4.26
Optical propertiesBiaxial (+)
Refractive indexnα = 2.3, nβ = 2.34, nγ = 2.38
Other characteristicsnon-radioactive, non-magnetic
References[1][2][3][4]

History

The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856).[2] Perovskite's notable crystal structure was first described by Victor Goldschmidt in 1926 in his work on tolerance factors.[7] The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw.[8]

Occurrence

Found in the Earth's mantle, perovskite's occurrence at Khibina Massif is restricted to the silica under-saturated ultramafic rocks and foidolites, due to the instability in a paragenesis with feldspar. Perovskite occurs as small anhedral to subhedral crystals filling interstices between the rock-forming silicates.[9]

Perovskite is found in contact carbonate skarns at Magnet Cove, Arkansas, in altered blocks of limestone ejected from Mount Vesuvius, in chlorite and talc schist in the Urals and Switzerland,[10] and as an accessory mineral in alkaline and mafic igneous rocks, nepheline syenite, melilitite, kimberlites and rare carbonatites. Perovskite is a common mineral in the Ca-Al-rich inclusions found in some chondritic meteorites.[3]

A rare-earth-bearing variety knopite ((Ca,Ce,Na)(Ti,Fe)O3) is found in alkali intrusive rocks in the Kola Peninsula and near Alnö, Sweden. A niobium-bearing variety dysanalyte occurs in carbonatite near Schelingen, Kaiserstuhl, Germany.[10][11]

In stars and brown dwarfs

In stars and brown dwarfs the formation of perovskite grains are responsible for the depletion of titanium oxide in the photosphere. Stars with a low temperature have dominant bands of TiO in their spectrum; as the temperature gets lower for stars and brown dwarfs with an even lower mass, CaTiO3 forms and at temperatures below 2000 K TiO is undetectable. The presence of TiO is used to define the transition between cool M-dwarf stars and the colder L-dwarfs.[12][13]

Special characteristics

The stability of perovskite in igneous rocks is limited by its reaction relation with sphene. In volcanic rocks perovskite and sphene are not found together, the only exception being an etindite from Cameroon.[14]

Physical properties

Perovskites have a cubic structure with general formula of ABO
3. In this structure, an A-site ion, on the corners of the lattice, is usually an alkaline earth or rare-earth element. B-site ions, on the center of the lattice, could be 3d, 4d, and 5d transition metal elements. A large number of metallic elements are stable in the perovskite structure, if the Goldschmidt's tolerance factor is in the range of 0.75–1.0.[15]

where RA, RB and RO are the ionic radii of A and B site elements and oxygen, respectively.

Perovskites have sub-metallic to metallic luster, colorless streak, cube like structure along with imperfect cleavage and brittle tenacity. Colors include black, brown, gray, orange to yellow. Crystals of perovskite appear as cubes, but are pseudocubic and crystallize in the orthorhombic system. Perovskite crystals have been mistaken for galena; however, galena has a better metallic luster, greater density, perfect cleavage and true cubic symmetry.[16]

See also

References
  1. Prehnit (Prehnite). Mineralienatlas.de
  2. Perovskite. Webmineral
  3. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W. and Nichols, Monte C. (Eds.) Perovskite. Handbook of Mineralogy. Mineralogical Society of America, Chantilly, VA.
  4. Inoue, Naoki and Zou, Yanhui (2006) Physical properties of perovskite-type lithium ionic conductor. Ch. 8 in Takashi Sakuma and Haruyuki Takahashi (Eds.) Physics of Solid State Ionics. pp. 247–269 ISBN 978-81-308-0070-7.
  5. Wenk, Hans-Rudolf; Bulakh, Andrei (2004). Minerals: Their Constitution and Origin. New York, NY: Cambridge University Press. p. 413. ISBN 978-0-521-52958-7.
  6. Szuromi, Phillip; Grocholski, Brent (2017). "Natural and engineered perovskites". Science. 358 (6364): 732–733. Bibcode:2017Sci...358..732S. doi:10.1126/science.358.6364.732. PMID 29123058.
  7. Golschmidt, V. M. (1926). "Die Gesetze der Krystallochemie". Die Naturwissenschaften. 14 (21): 477–485. Bibcode:1926NW.....14..477G. doi:10.1007/BF01507527.
  8. Megaw, Helen (1945). "Crystal Structure of Barium Titanate". Nature. 155 (3938): 484–485. Bibcode:1945Natur.155..484.. doi:10.1038/155484b0.
  9. Chakhmouradian, Anton R.; Mitchell, Roger H. (1998). "Compositional variation of perovskite-group minerals from the Khibina Complex, Kola Peninsula, Russia" (PDF). The Canadian Mineralogist. 36: 953–969.
  10. Palache, Charles, Harry Berman and Clifford Frondel, 1944, Dana's System of Mineralogy Vol. 1, Wiley, 7th ed. p. 733
  11. Deer, William Alexander; Howie, Robert Andrew; Zussman, J. (1992). An introduction to the rock-forming minerals. Longman Scientific Technical. ISBN 978-0-582-30094-1.
  12. Allard, France; Hauschildt, Peter H.; Alexander, David R.; Tamanai, Akemi; Schweitzer, Andreas (July 2001). "The Limiting Effects of Dust in Brown Dwarf Model Atmospheres". Astrophysical Journal. 556 (1): 357–372. arXiv:astro-ph/0104256. Bibcode:2001ApJ...556..357A. doi:10.1086/321547. ISSN 0004-637X.
  13. Kirkpatrick, J. Davy; Allard, France; Bida, Tom; Zuckerman, Ben; Becklin, E. E.; Chabrier, Gilles; Baraffe, Isabelle (July 1999). "An Improved Optical Spectrum and New Model FITS of the Likely Brown Dwarf GD 165B". Astrophysical Journal. 519 (2): 834–843. Bibcode:1999ApJ...519..834K. doi:10.1086/307380. ISSN 0004-637X.
  14. Veksler, I. V.; Teptelev, M. P. (1990). "Conditions for crystallization and concentration of perovskite-type minerals in alkaline magmas". Lithos. 26 (1): 177–189. Bibcode:1990Litho..26..177V. doi:10.1016/0024-4937(90)90047-5.
  15. Peña, M. A.; Fierro, J. L. (2001). "Chemical structures and performance of perovskite oxides" (PDF). Chemical Reviews. 101 (7): 1981–2017. doi:10.1021/cr980129f. PMID 11710238.
  16. Luxová, Jana; Šulcová, Petra; Trojan, M. (2008). "Study of Perovskite" (PDF). Journal of Thermal Analysis and Calorimetry. 93 (3): 823–827. doi:10.1007/s10973-008-9329-z.
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