Perovskite
Perovskite (pronunciation: /pəˈrɒvskaɪt/) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula CaTiO3). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO3, known as the perovskite structure, which has a general chemical formula A2+B4+(X2−)3.[6] Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.[7]
This article is about the mineral. For synthetic compounds, see Perovskite (structure). For solar cells using perovskite-structured compounds, see Perovskite solar cell.Perovskite
CaTiO3
Prv[1]
4.CC.30
Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Pbnm
135.96 g/mol
Black, reddish brown, pale yellow, yellowish orange
Pseudo cubic – crystals show a cubic outline
complex penetration twins
[100] good, [010] good, [001] good
Conchoidal
5.0–5.5
Adamantine to metallic; may be dull
grayish white
Transparent to opaque
3.98–4.26
Biaxial (+)
nα = 2.3, nβ = 2.34, nγ = 2.38
non-radioactive, non-magnetic
History[edit]
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).[3] Perovskite's notable crystal structure was first described by Victor Goldschmidt in 1926 in his work on tolerance factors.[8] The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw.[9]
Perovskite derivatives[edit]
Double perovskites[edit]
A double perovskite has a formula of A'A"B'B"O6 and replaces half the B sites with B′, where A are alkaline or rare earth metals and B are transition metals. The cation arrangement will differ based on charge, coordination geometry, and the ratio between A cation and B cation radii. The B and B′ cations lead to different ordering schemes. These ordering schemes are rock salt, columnar, and layered structures.[20] Rock salt is an alternating, three-dimensional checkerboard of B and B' polyhedra. This structure is the most common from an electrostatic point of view, as the B sites will have different valence states. Columnar arrangement can be viewed as sheets of B-cation polyhedral viewed from the [111] direction. Layered structures are seen as sheets of B′ and B polyhedra.
Lower dimensional perovskites[edit]
3D perovskites form when there is a smaller cation in the A site so BX6 octahedra can be corner shared. 2D perovskites form when the A-site cation is larger so octahedra sheets are formed. In 1D perovskites, a chain of octahedra is formed[21] while in 0D perovskites, individual octahedra are separated from each other. Both 1D and 0D perovskites lead to quantum confinement[22] and are investigated for lead-free perovskite solar cell materials.[23]
