perovskitestructure

Perovskite structure refers to a class of crystalline materials that share the same topology as the mineral perovskite, CaTiO3. The general chemical formula is ABX3, where A is a larger cation, B is a smaller cation, and X is an anion. In the corner-connected three-dimensional framework, BX6 octahedra form a network that runs throughout the crystal, while A-site cations occupy the interstitial sites between the octahedra. In the ideal cubic archetype, B sits at the body center of the cell, X anions lie at face centers, and A cations sit at the cube corners, giving the space group Pm3m.

Stability of the structure depends on ionic sizes. The Goldschmidt tolerance factor t = (r_A + r_X) / [√2 (r_B + r_X)]. Values near 1 favor a cubic lattice; smaller or larger t induce tilts of the BX6 octahedra and lower-symmetry distortions such as tetragonal or orthorhombic structures. These tilts are often described by Glazer notation.

The class includes oxide perovskites with the formula ABX3 (X = O2−), such as CaTiO3, SrTiO3, and BaTiO3, and halide or hybrid perovskites in which X is a halide (I−, Br−, Cl−) and A is an organic or inorganic cation, with B commonly Pb2+ or Sn2+. Hybrid variants may have organic A-site cations such as methylammonium or formamidinium.

The perovskite framework yields properties including high dielectric constants, adjustable band gaps, and, in halide variants, strong light absorption and charge transport. These features drive applications in photovoltaics, LEDs, sensors, and catalysis. The term derives from the mineral perovskite, named after the Russian mineralogist Lev Perovski.