Titanate
A titanate is a mixed oxide containing titanium in the +4 oxidation state. Titanates form with a wide variety of metals and differing stoichiometries (including non-stoichiometric compounds).[1] Although the terms orthotitanate and metatitanate have been used to refer to MxTiO4 and MxTiO3 stoichiometries respectively, only barium orthotitanate, Ba2TiO4, contains discrete titanium oxoanions.[1][2] The name "titanic acid" has sometimes been applied to hydrated titanium dioxide.
Many titanates, especially barium titanate, BaTiO3, have been extensively studied for their ferroelectric and piezoelectric properties.[1]
Structural types
The titanates of bivalent cations, MIITiO3, can be divided into two structural types, which are shared by many other mixed oxides.
- Ilmenite structure
- With medium-sized cations, the type structure is that of ilmenite, FeTiO3, with hexagonal close-packing of the oxide ions and one-third of the octahedral holes occupied by each of M2+ and Ti4+.
- Perovskite structure
- With large cations, the type structure is that of perovskite, CaTiO3: this can be viewed as a halite-type lattice (cubic close-packing) of M2+ and oxide ions, with the Ti4+ ions sitting in octahedral holes formed only by oxide ions.
Titanates of the formula MII2TiO4 often adopt the spinel structure when M2+ is medium sized.
See also
Notes and references
Notes
References
- ↑ 1.0 1.1 1.2 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1121–23. ISBN 0-08-022057-6.
- ↑ Bland, J. A. The crystal structure of barium orthotitanate, Ba2TiO4. Acta Crystallogr. 1961, 14, 875–81. DOI: 10.1107/S0365110X61002527.
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