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'Perovskite' (calcium titanium oxide, CaTiO₃) is a relatively rare mineral on the Earth's crust. Perovskite crystallizes in the orthorhombic (pseudocubic) crystal system. 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).
Perovskite is also the name of a more general group of crystals which take the same structure. The basic chemical formula follows the pattern ABO₃, where A and B are cations of different sizes (for example, LaMnO₃). Formed under the high pressure conditions of the Earth's mantle, the pyroxene enstatite (MgSiO₃) is a perovskite-structured polymorph which may be the most common mineral in the Earth.^[1]

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Structure

References

See also

External links

Structure

The perovskite structure is adopted by many oxides that have the chemical formula ABO₃. The structure is very versatile having many useful technological applications such as ferroelectrics, catalysts, sensors and superconductors.
The general crystal structure is a primitive cube, with the A-cation in the middle of the cube, the B-cation in the corner and the anion, commonly oxygen, in the centre of the face edges. The structure is stabilized by the 6 coordination of the B-cation (octahedron) and 12 of the A cation. The packing of the ions can be thought of the A and O ions together form a cubic close packed array, where the B ions occupy a quarter of the octahedral holes.
Although the primitive cube is the idealized structure, differences in radius between the A and B cations can alter the structure to a number of different so-called distortions, of which tilting is the most common one. With perovskite tilt the BO6 octahedron twists along one or more axes to accommodate the difference.
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.

References

1. QI: The Book of General Ignorance, , , John Lloyd, Faber & Faber, ,


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See also

★ Diamond anvil

★ List of minerals

★ List of minerals named after people

External links

★ perovskites at NCSU