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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 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 is a perovskite-structured polymorph of MgSiO3, and may be the most common mineral in the Earth.
Perovskite materials are used as catalyst electrodes in certain types of fuel cells.
Additional recommended knowledge
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 B cation in the middle of the cube, the A cation in the corner and the anion, commonly oxygen, in the centre of the face edges. The structure is stabilized by the 6-fold coordination of the B cation (octahedron) and 12-fold coordination of the A cation. The packing of the ions can be thought of as the A and O ions together forming a cubic close-packed array, where the B ions occupy a quarter of the octahedral spaces.
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.
Perovskite also is a common mineral in the Ca-Al-rich inclusions (CAIs) found in some chondritic meteorites.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Perovskite". A list of authors is available in Wikipedia.|