Titanate

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In chemistry, titanate usually refers to inorganic compounds composed of titanium oxides, or oxides containing the titanium element. Together with niobate, titanate salts form the Perovskite group.

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In some cases, the term is used more generally for any titanium-containing anion, e.g. [TiCl6]2− and [Ti(CO)6]2−. 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 tube furnaces, from titanium dioxide. In virtually all cases, titanium achieves octahedral coordination geometry. [1]

Orthotitanates

Orthotitanates have the formula M2TiO4, where M is divalent. An example of such a material is magnesium titanate (Mg2TiO4), which adopts the spinel structure. Li2TiO3 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 TiO44− centres, an exception being Ba2TiO4. [2]

Titanic acid and its esters

Also called orthotitanic acid or titanium hydroxide, the substance H4TiO4 is called titanic acid. This material, which is not well defined, is obtained by hydrolysis of TiCl4. [3] 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. Ti4(OCH3)16 or titanium tetramethoxide. [4] It is a weak acid, if it can be isolated.

Metatitanates

The metatitanates have the formula MTiO3, where again M is divalent. They do not feature discrete TiO32− centres. Some, like the commercially important mineral ilmenite (FeTiO3), crystallize in the hexagonal close packing motif seen in corundum. Alternatively, some materials with the formula MTiO3 crystallize in the motif known as perovskite, which is also the name of the mineral form of calcium titanate (CaTiO3). Barium titanate is one such perovskite-structured titanate with ferroelectric properties. [1]

Complex titanates

More complex titanates are also known, such as bismuth titanate, Bi4Ti3O12. [5]

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<span class="mw-page-title-main">Perovskite (structure)</span> Type of crystal structure

A perovskite is any material with a crystal structure following the formula ABX3, which was first discovered as the mineral called perovskite, which consists of calcium titanium oxide (CaTiO3). The mineral was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and named after Russian mineralogist L. A. Perovski (1792–1856). 'A' and 'B' are two positively charged ions (i.e. cations), often of very different sizes, and X is a negatively charged ion (an anion, frequently oxide) that bonds to both cations. The 'A' atoms are generally 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. Additional perovskite forms may exist where either/both the A and B sites have a configuration of A1x-1A2x and/or B1y-1B2y and the X may deviate from the ideal coordination configuration as ions within the A and B sites undergo changes in their oxidation states.

In chemistry, perxenates are salts of the yellow xenon-containing anion XeO4−
6. This anion has octahedral molecular geometry, as determined by Raman spectroscopy, having O–Xe–O bond angles varying between 87° and 93°. The Xe–O bond length was determined by X-ray crystallography to be 1.875 Å.

In chemistry, the term stannate or tinnate refers to compounds of tin (Sn). Stannic acid (Sn(OH)4), the formal precursor to stannates, does not exist and is actually a hydrate of SnO2. The term is also used in naming conventions as a suffix; for example the hexachlorostannate ion is SnCl2−
6.

In chemistry, an aluminate is a compound containing an oxyanion of aluminium, such as sodium aluminate. In the naming of inorganic compounds, it is a suffix that indicates a polyatomic anion with a central aluminium atom.

<span class="mw-page-title-main">Telluric acid</span> Chemical compound (Te(OH)6)

Telluric acid, or more accurately Orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution. In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules, containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide. Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water. It is used as tellurium-source in the synthesis of oxidation catalysts.

In chemistry, a plumbate often refers to compounds that can be viewed as derivatives of the hypothetical PbO2−3 anion. The term also refers to any anion of lead or any salt thereof. So the term is vague and somewhat archaic.

<span class="mw-page-title-main">Barium titanate</span> Chemical compound

Barium titanate (BTO) is an inorganic compound with chemical formula BaTiO3. Barium titanate appears white as a powder and is transparent when prepared as large crystals. It is a ferroelectric, pyroelectric, and piezoelectric ceramic material that exhibits the photorefractive effect. It is used in capacitors, electromechanical transducers and nonlinear optics.

<span class="mw-page-title-main">Titanium isopropoxide</span> Chemical compound

Titanium isopropoxide, also commonly referred to as titanium tetraisopropoxide or TTIP, is a chemical compound with the formula Ti{OCH(CH3)2}4. This alkoxide of titanium(IV) is used in organic synthesis and materials science. It is a diamagnetic tetrahedral molecule. Titanium isopropoxide is a component of the Sharpless epoxidation, a method for the synthesis of chiral epoxides.

Molybdenum dioxide is the chemical compound with the formula MoO2. It is a violet-colored solid and is a metallic conductor. The mineralogical form of this compound is called tugarinovite, and is only very rarely found.

<span class="mw-page-title-main">Barium ferrate</span> Chemical compound

Barium ferrate is the chemical compound of formula BaFeO4. This is a rare compound containing iron in the +6 oxidation state. The ferrate(VI) ion has two unpaired electrons, making it paramagnetic. It is isostructural with BaSO4, and contains the tetrahedral [FeO4]2− anion.

<span class="mw-page-title-main">Perovskite</span> Oxide mineral

Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula CaTiO3). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO3, known as the perovskite structure, which has a general chemical formula A2+B4+(X2−)3. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.

<span class="mw-page-title-main">Calcium titanate</span> Chemical compound

Calcium titanate is an inorganic compound with the chemical formula Ca Ti O3. As a mineral, it is called perovskite, named after Russian mineralogist, L. A. Perovski (1792-1856). It is a colourless, diamagnetic solid, although the mineral is often coloured owing to impurities.

<span class="mw-page-title-main">Germanate</span> Chemical compound

In chemistry, germanate is a compound containing an oxyanion of germanium. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central germanium atom, for example potassium hexafluorogermanate, K2GeF6.

<span class="mw-page-title-main">Sodium bismuthate</span> Chemical compound

Sodium bismuthate is an inorganic compound, and a strong oxidiser with chemical formula NaBiO3. It is somewhat hygroscopic, but not soluble in cold water, which can be convenient since the reagent can be easily removed after the reaction. It is one of the few water insoluble sodium salts. Commercial samples may be a mixture of bismuth(V) oxide, sodium carbonate and sodium peroxide.

<span class="mw-page-title-main">Calcium copper titanate</span> Chemical compound

Calcium copper titanate (also abbreviated CCTO, for calcium copper titanium oxide) is an inorganic compound with the formula CaCu3Ti4O12. It is noteworthy for its extremely large dielectric constant (effective relative permittivity) of over 10,000 at room temperature.

Barium orthotitanate is the inorganic compound with the chemical formula Ba2TiO4. It is a colourless solid that is of interest because of its relationship to barium titanate, a useful electroceramic.

Sodium bismuth titanate or bismuth sodium titanium oxide (NBT or BNT) is a solid inorganic compound of sodium, bismuth, titanium and oxygen with the chemical formula of Na0.5Bi0.5TiO3 or Bi0.5Na0.5TiO3. This compound adopts the perovskite structure.

<span class="mw-page-title-main">Titanyl sulfate</span> Chemical compound

Titanyl sulfate is the inorganic compound with the formula TiOSO4. It is a white solid that forms by treatment of titanium dioxide with fuming sulfuric acid. It hydrolyzes to a gel of hydrated titanium dioxide. The structure consists of dense polymeric network with tetrahedral sulfur and octahedral titanium centers. The six ligands attached to titanium are derived from four different sulfate moieties and a bridging oxide. A monohydrate is also known, being prepared similarly to the anhydrous material. In the hydrate, one Ti–OS bond is replaced by Ti–OH2.

The +4 oxidation state dominates titanium chemistry, but compounds in the +3 oxidation state are also numerous. Commonly, titanium adopts an octahedral coordination geometry in its complexes, but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding.

References

  1. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1121–23. ISBN   978-0-08-022057-4..
  2. ↑ Wu, Kang Kun; Brown, I. D. (10 April 1973). "The Crystal Structure of β-Barium Orthotitanate, β-Ba2TiO4, and the Bond Strength-Bond Length Curve of Ti-O". Acta Crystallographica. B29: 2009–2012. doi:10.1107/S0567740873005959.
  3. ↑ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 421.
  4. ↑ D. A. Wright and D. A. Williams "The crystal and molecular structure of titanium tetramethoxide" Acta Crystallogr. B 1968, volume 24, pp. 1107-1114. doi : 10.1107/S0567740868003766.
  5. ↑ Galasso, F. S.; Kestigan, M. (2007), "Bismuth Titanate, Bi4Ti3O12", Inorg. Synth., 30: 121, doi:10.1002/9780470132616.ch24 .
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