# 
Titanium dioxide

By [OTESs11T](https://paragraph.com/@otess11t) · 2023-05-30

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**Titanium dioxide**, also known as **titanium(IV) oxide** or **titania** [/taɪˈteɪniə/](https://en.wikipedia.org/wiki/Help:IPA/English), is the [inorganic compound](https://en.wikipedia.org/wiki/Inorganic_compound) with the chemical formula TiO 2. When used as a [pigment](https://en.wikipedia.org/wiki/Pigment), it is called **titanium white**, **Pigment White 6** (**PW6**), or [**CI 77891**](https://en.wikipedia.org/wiki/Colour_Index_International).[\[4\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-Ullmann-4) It is a white solid that is insoluble in water, although mineral forms can appear black. As a pigment, it has a wide range of applications, including [paint](https://en.wikipedia.org/wiki/Paint), [sunscreen](https://en.wikipedia.org/wiki/Sunscreen), and [food coloring](https://en.wikipedia.org/wiki/Food_coloring). When used as a food coloring, it has [E number](https://en.wikipedia.org/wiki/E_number) E171. World production in 2014 exceeded 9 million tonnes.[\[5\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-5)[\[6\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-6)[\[7\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-7) It has been estimated that titanium dioxide is used in two-thirds of all pigments, and pigments based on the oxide have been valued at a price of $13.2 billion.[\[8\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-8)

Structure
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In all three of its main dioxides, [titanium](https://en.wikipedia.org/wiki/Titanium) exhibits octahedral geometry, being bonded to six oxide anions. The oxides in turn are bonded to three Ti centers. The overall crystal structures of rutile and anatase are tetragonal in symmetry whereas brookite is orthorhombic. The oxygen substructures are all slight distortions of [close packing](https://en.wikipedia.org/wiki/Close_packing): in rutile, the oxide anions are arranged in distorted hexagonal close-packing, whereas they are close to cubic close-packing in anatase and to "double hexagonal close-packing" for brookite. The [rutile structure](https://en.wikipedia.org/wiki/Rutile_structure) is widespread for other metal dioxides and difluorides, e.g. RuO2 and ZnF2.

Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms.[\[9\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-Ald-9) This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms.

Structure of [anatase](https://en.wikipedia.org/wiki/Anatase). Together with rutile and brookite, one of the three major [polymorphs](https://en.wikipedia.org/wiki/Polymorphism_\(materials_science\)) of TiO2.

Production and occurrence
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Synthetic TiO2 is mainly produced from the mineral [ilmenite](https://en.wikipedia.org/wiki/Ilmenite). [Rutile](https://en.wikipedia.org/wiki/Rutile), and [anatase](https://en.wikipedia.org/wiki/Anatase), naturally occurring TiO2, occur widely also, e.g. rutile as a 'heavy mineral' in beach sand. [Leucoxene](https://en.wikipedia.org/wiki/Leucoxene), fine-grained anatase formed by natural alteration of ilmenite, is yet another ore. [Star sapphires](https://en.wikipedia.org/wiki/Star_sapphire_\(jewel\)) and [rubies](https://en.wikipedia.org/wiki/Ruby) get their [asterism](https://en.wikipedia.org/wiki/Asterism_\(gemology\)) from oriented inclusions of rutile needles.[\[10\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-BuildingBlocks451-3-10)

### Mineralogy and uncommon polymorphs

Titanium dioxide occurs in nature as the minerals [rutile](https://en.wikipedia.org/wiki/Rutile) and [anatase](https://en.wikipedia.org/wiki/Anatase). Additionally two high-pressure forms are known minerals: a [monoclinic](https://en.wikipedia.org/wiki/Monoclinic_crystal_system) [baddeleyite](https://en.wikipedia.org/wiki/Baddeleyite)\-like form known as [akaogiite](https://en.wikipedia.org/wiki/Akaogiite), and the other has a slight monoclinic distortion of the [orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system) [α-PbO2](https://en.wikipedia.org/wiki/Lead_dioxide) structure and is known as [riesite](https://en.wikipedia.org/w/index.php?title=Riesite&action=edit&redlink=1). Both of which can be found at the [Ries crater](https://en.wikipedia.org/wiki/N%C3%B6rdlinger_Ries) in [Bavaria](https://en.wikipedia.org/wiki/Bavaria).[\[11\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-11)[\[12\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-12)[\[13\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-13) It is mainly sourced from [ilmenite](https://en.wikipedia.org/wiki/Ilmenite), which is the most widespread titanium dioxide-bearing ore around the world. Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. The metastable anatase and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C (1,110–1,470 °F).[\[14\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-Greenwood-14)

Titanium dioxide has twelve known polymorphs – in addition to rutile, anatase, brookite, akaogiite and riesite, three metastable phases can be produced synthetically ([monoclinic](https://en.wikipedia.org/wiki/Monoclinic_crystal_system), [tetragonal](https://en.wikipedia.org/wiki/Tetragonal_crystal_system), and orthorhombic ramsdellite-like), and four high-pressure forms (α-PbO2-like, [cotunnite](https://en.wikipedia.org/wiki/Cotunnite)\-like, orthorhombic OI, and cubic phases) also exist:

FormCrystal systemSynthesis[Rutile](https://en.wikipedia.org/wiki/Rutile)[Tetragonal](https://en.wikipedia.org/wiki/Tetragonal_crystal_system)[Anatase](https://en.wikipedia.org/wiki/Anatase)[Tetragonal](https://en.wikipedia.org/wiki/Tetragonal_crystal_system)[Brookite](https://en.wikipedia.org/wiki/Brookite)[Orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system)TiO2(B)[\[15\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-15)[Monoclinic](https://en.wikipedia.org/wiki/Monoclinic_crystal_system)Hydrolysis of K2Ti4O9 followed by heatingTiO2(H), [hollandite](https://en.wikipedia.org/wiki/Hollandite)\-like form[\[16\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-16)[Tetragonal](https://en.wikipedia.org/wiki/Tetragonal_crystal_system)Oxidation of the related potassium titanate bronze, K0.25TiO2TiO2(R), [ramsdellite](https://en.wikipedia.org/wiki/Ramsdellite)\-like form[\[17\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-17)[Orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system)Oxidation of the related lithium titanate bronze Li0.5TiO2TiO2(II)-([α-PbO2](https://en.wikipedia.org/wiki/Lead_dioxide)\-like form)[\[18\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-18)[Orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system)[Akaogiite](https://en.wikipedia.org/wiki/Akaogiite) ([baddeleyite](https://en.wikipedia.org/wiki/Baddeleyite)\-like form, 7 coordinated Ti)[\[19\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-19)[Monoclinic](https://en.wikipedia.org/wiki/Monoclinic_crystal_system)TiO2 -OI[\[20\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-20)[Orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system)[Cubic](https://en.wikipedia.org/wiki/Cubic_crystal_system) form[\[21\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-21)[Cubic](https://en.wikipedia.org/wiki/Cubic_crystal_system)P > 40 GPa, T > 1600 °CTiO2 -OII, [cotunnite](https://en.wikipedia.org/wiki/Cotunnite)([PbCl2](https://en.wikipedia.org/wiki/Lead\(II\)_chloride))-like[\[22\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-du1-22)[Orthorhombic](https://en.wikipedia.org/wiki/Orthorhombic_crystal_system)P > 40 GPa, T > 700 °C

The [cotunnite](https://en.wikipedia.org/wiki/Cotunnite)\-type phase was claimed to be the hardest known oxide with the [Vickers hardness](https://en.wikipedia.org/wiki/Vickers_hardness) of 38 GPa and the [bulk modulus](https://en.wikipedia.org/wiki/Bulk_modulus) of 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure.[\[22\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-du1-22) However, later studies came to different conclusions with much lower values for both the hardness (7–20 GPa, which makes it softer than common oxides like corundum Al2O3 and rutile TiO2)[\[23\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-23) and bulk modulus (~300 GPa).[\[24\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-24)[\[25\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-25)

Titanium dioxide (B) is found as a [mineral](https://en.wikipedia.org/wiki/Mineral) in magmatic rocks and hydrothermal veins, as well as weathering rims on [perovskite](https://en.wikipedia.org/wiki/Perovskite). TiO2 also forms [lamellae](https://en.wikipedia.org/wiki/Lamella_\(materials\)) in other minerals.[\[26\]](https://en.wikipedia.org/wiki/Titanium_dioxide#cite_note-26)

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