perovskite

(redirected from Perovskite structure)
Also found in: Dictionary.
Related to Perovskite structure: Spinel structure

perovskite

[pə′rävz‚kīt]
(mineralogy)
Ca[TiO3] A natural, yellow, brownish-yellow, reddish, brown, or black mineral and a structure type which includes no less than 150 synthetic compounds; the crystal structure is ideally cubic, it occurs as rounded cubes modified by the octahedral and dodecahedral forms, luster is subadamantine to submetallic, hardness is 5.5 on Mohs scale, and specific gravity is 4.0.

Perovskite

 

(named for L. A. Perovskii). (1) A mineral of the oxide class. The chemical formula of perovskite is CaTiO3, with CaO accounting for 41.24 percent of the composition, and TiO2 for 58.76 percent. Perovskite that contains admixtures of Ce is called knopite; of Ni, Ce, and Fe, dysanalite; and of Na, Ce, Ti, and Nb, loparite.

Perovskite crystallizes in the pseudoisometric system. Each calcium atom is surrounded by 12 oxygen atoms, which are located at the apexes of a cuboctahedron; the coordination number of Ti is eight. Characteristic striations appear on the cubic faces parallel to the edges. Cleavage is cubic, hardness is 5.5–6 on Mohs’ scale, and the density ranges from 3,950 to 4,040 kg/m3. The color may be black, grayish black, or brownish.

Perovskite frequently occurs in ultrabasic alkaline rocks, including olivinites, pyroxenes, and kimberlites, as well as in associated ore segregations and carbonatites. It fills the interstices at the point of contact of basic rocks with limestone; it also is interstitially distributed in chloritic shale and in nephelinic, leu-citic, and melilitic basalts.

Knopite is used as a source of rare-earth elements of the cerium group, and loparite is a source of niobium and titanium.

(2) A group of chemical compounds whose crystal structure resembles that of perovskite [in English usage “perovskite” is the adjectival noun that denotes the structure type of these compounds and not the compounds themselves]. Perovskites have the general formula ABX3, where A is a tetravalent cation, B is a heptavalent cation, and X is an anion—usually oxygen, as in NaNbO3 and BaTiO3. Many of these compounds are ferroelectric, including BaTiO3 and LiNbO3; the group also includes some superconductors (for example, SrTiO3), semiconductors, and compounds that display magnetic ordering.

perovskite

An oxide mineral made up of calcium titanate that is expected to be commercialized in higher-efficiency solar cells in the 2020-2021 time frame. Named after Russian mineralogist Lev Perovski, who discovered it in the 1800s, perovskite may also be employed as quantum dots in future screen technologies due to its high color purity. See quantum dot.

Automatic Solar Cell Window Shades
In 2018, using perovskite and carbon nanotube technologies, the National Renewable Energy Lab in Golden, Colorado developed clear window glass that emits electricity and darkens with sunshine. When the sun fades, the window becomes transparent again. The transparency range is 3% to 68%.
References in periodicals archive ?
The experiment determined the magnetic structure of Sr2IrO4, in particular the orientation of the magnetic moments in its layered perovskite structure. In the process, the analysis of the NRS data led to the surprising discovery of an unexpected component of the magnetic moments, which is probably attributable to a deficiency of oxygen atoms in the crystal structure.
This phase transition is caused by a change in the lattice parameters (c and a) of the perovskite structure. The addition of Sr in the PT matrix gradually increases the a-axis and decreases the c-axis resulting in a lower unit-cell volume [19-24].
Xing, "Thermogravimetric study on oxygen adsorption/desorption properties of double perovskite structure oxides REBa[Co.sub.2][O.sub.5+[delta]] (RE = Pr, Gd, Y)," Journal of Rare Earths, vol.
When the doping amount is more than 30%, two phases of perovskite structure [Sr.sub.1-x][K.sub.x]Ti[O.sub.3-[delta]] and Ti[O.sub.2] are formed, which may cause the SSA to decrease.
In addition, ferromagnetism appears after oxygen depletion, which has been confirmed for other materials with AB[O.sub.3] perovskite structure [35, 36].
That is typical for the M-O (possible La-O and Al-O stretching frequencies) vibration for perovskite structure [19].
Bismuth iron oxide crystallizes in rhombohedrally distorted perovskite structure. It exhibits G-type antiferromagnetic behavior.
The main hurdle in the PT fabrication is the synthesis of a single phase with required perovskite structure. The primary difficulty is due to the volatility of PbO at elevated temperatures.
It's well known that the crystal formation of PZT is perovskite structure, and its basic unit is oxygen octahedral structure.
This suggestion is corroborated by the discovery of superconductivity at 8 K in the intermetallic compound [MgCNi.sub.3], which has the perovskite structure (9).
This proposal seeks to address these challenges by developing new materials based on a structure related to the state-of-the-art materials: the double perovskite structure. Here, the lead atoms are replaced by alternating non-toxic alternatives which are air stable elements and can be processed from solution.