FERROELECTRICITY AND THE CHEMICAL BOND IN PEROVSKITE-TYPE OXIDES
Abstract
A molecular-orbital approach provides insight into the nature of the occurrence of ferroelectricity and antiferroelectricity in perovskite type oxides. The formation of pi bonds, in addition to the sigma bonds in BaTiO3 structures and isomorphous compounds, leads to a strong mutual interaction along a chain. The absence or presence of pi bonding perpendicular to the axis of the strong interaction leads to chain alignments that are ferroelectric or antiferro electric, respectively. The role played by the cuboctahedral-coordinated cation is described. Comparison of the environment of a cation in acid solution and in perovskite-type oxides reveals great similarity of bonding. By application of group-theoretical methods, a symmetry classification of orbitals is derived for each molecular point group occurring in BaTiO3. Molecular orbital energy-level diagrams are constructed. The number and classification of the electronic transitions are predicted by means of the selection rules. It is shown that only ions with empty d shells are capable of forming ferro- and antiferroelectric perovskite-type oxides. A discussion of conductivity in these materials is given.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1963
- Accession Number
- AD0406722
Entities
People
- Carl W. Nelson
Organizations
- Massachusetts Institute of Technology