In
chemistry,
titanate usually refers to inorganic compounds composed of
, or
containing the
titanium element. Together with
niobate, titanate salts form the Perovskite group.
In some cases, the term is used more generally for any titanium-containing anion, e.g. TiCl62− and Ti(CO)62−. This article focuses on the oxides.
Many kinds of titanium oxides are known, and some are commercially important. Typically these materials are white, diamagnetic, high-melting, and insoluble in water. They are often prepared at high temperatures, e.g. using , from titanium dioxide. In virtually all cases, titanium achieves octahedral coordination geometry.[.]
Orthotitanates
Orthotitanates have the formula M
2TiO
4, where M is divalent. An example of such a material is magnesium titanate (Mg
2TiO
4), which adopts the
Spinel group. Li
2TiO
3 is not considered an orthotitanate since it adopts the rock-salt structure and does not feature an identifiable titanium anion. Orthotitanates almost never feature identifiable TiO
44− centres, an exception being Ba
2TiO
4.
Titanic acid and its esters
Also called orthotitanic acid or titanium hydroxide, the substance H
4TiO
4 is called
titanic acid. This material, which is not well defined, is obtained by hydrolysis of TiCl
4.
[Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 421.] The solid is unstable with respect to loss of water and formation of titanium dioxide.
Esters of orthotitanic acid are known, however; one example being titanium isopropoxide. Esters derived from smaller alcohols adopt more complex structures wherein titanium does achieve octahedral coordination, e.g. Ti
4(OCH
3)
16 or titanium tetramethoxide.
[D. A. Wright and D. A. Williams "The crystal and molecular structure of titanium tetramethoxide" Acta Crystallogr. B 1968, volume 24, pp. 1107-1114. .] It is a weak acid, if it can be isolated.
Metatitanates
The metatitanates have the formula MTiO
3, where again M is divalent. They do not feature discrete TiO
32− centres. Some, like the commercially important mineral
ilmenite (FeTiO
3), crystallize in the hexagonal close packing motif seen in
corundum. Alternatively, some materials with the formula MTiO
3 crystallize in the motif known as perovskite, which is also the name of the mineral form of
calcium titanate (CaTiO
3).
Barium titanate is one such perovskite-structured titanate with
ferroelectric properties.
Complex titanates
More complex titanates are also known, such as
bismuth titanate, Bi
4Ti
3O
12.
[.]
