
Perovskite (Structure) - peter_d_sherman
https://en.wikipedia.org/wiki/Perovskite_(structure)
======
peter_d_sherman
>"A perovskite is any material with the same type of crystal structure as
calcium titanium oxide (CaTiO3), known as the perovskite structure."

[...]

"The general chemical formula for perovskite compounds is ABX3, where 'A' and
'B' are two cations of very different sizes, and X is an anion that bonds to
both. The 'A' atoms are larger than the 'B' atoms. The ideal cubic structure
has the B cation in 6-fold coordination, surrounded by an octahedron of
anions, and the A cation in 12-fold cuboctahedral coordination."

[...]

"The perovskite structure is adopted by many oxides that have the chemical
formula ABO3."

[...]

"Perovskites can be deposited as epitaxial thin films on top of other
perovskites,[10] using techniques such as pulsed laser deposition and
molecular-beam epitaxy. These films can be a couple of nanometres thick or as
small as a single unit cell.[11] The well-defined and unique structures at the
interfaces between the film and substrate can be used for interface
engineering, where new types properties can arise.[12] This can happen through
several mechanisms, from mismatch strain between the substrate and film,
change in the oxygen octahedral rotation, compositional changes, and quantum
confinement.[13] An example of this is LaAlO3 grown on SrTiO3, where the
interface can exhibit conductivity, even though both LaAlO3 and SrTiO3 is non-
conductive.[14]"

[...]

"Perovskite materials exhibit many interesting and intriguing properties from
both the theoretical and the application point of view. Colossal
magnetoresistance, ferroelectricity, superconductivity, charge ordering, spin
dependent transport, high thermopower and the interplay of structural,
magnetic and transport properties are commonly observed features in this
family. These compounds are used as sensors and catalyst electrodes in certain
types of fuel cells[16] and are candidates for memory devices and spintronics
applications.[17]

Many superconducting ceramic materials (the high temperature superconductors)
have perovskite-like structures, often with 3 or more metals including copper,
and some oxygen positions left vacant. One prime example is yttrium barium
copper oxide which can be insulating or superconducting depending on the
oxygen content."

