Perovskite
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Perovskite (calcium titanium oxide, CaTiO3) is a relatively rare mineral occurring in orthorhombic (pseudocubic) crystals. Perovskite is found in contact metamorphic rocks and associated mafic intrusives, nepheline syenites, and rare carbonatites. Perovskite was discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named for Russian mineralogist, L. A. Perovski (1792-1856).
Under the high pressure conditions of the mantle the pyroxene enstatite, MgSiO3, is a perovskite polymorph and may be the most common mineral in the Earth.
Perovskite is also the name of a more general group of crystals which take the same structure. See perovskite structure for details. The basic chemical formula follows the pattern ABO3, where A and B are cations of different sizes (for example, LaMnO3).The idealized structure is primitive cube, but differences in ratio between the A and B cations can distort the structure to a number of different so-called distortions, of which tilting is the most common one. The B-cations are located at the corners of the unit cell with A in the centre. The oxygen ions are at the centres of each edge of the unit cell.
Complex perovskite structures contain two different B-site cations. This results in ordered and disordered variants.
The perovskite structure shares the property of ferroelectricity with garnet and olivine. Many superconducting ceramic materials have perovskite-like structures.
[edit] References
Tejuca, Luis G. (1993). Properties and applications of perovskite-type oxides. New York: Dekker, 382. ISBN 0-8247-8786-2.
