Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound derived from titanium with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. 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, sunscreen, and food coloring. When used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million tonnes."Titanium" in 2014 Minerals Yearbook. USGS 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.
Structure
In all three of its main dioxides, 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: 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 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. This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms.
Synthetic and geologic occurrence Synthetic TiO2 is mainly produced from the mineral ilmenite. Rutile, and anatase, naturally occurring TiO2, occur widely also, e.g. rutile as a 'heavy mineral' in beach sand. Leucoxene, fine-grained anatase formed by natural alteration of ilmenite, is yet another ore. Star sapphires and rubies get their asterism from oriented inclusions of rutile needles.
Mineralogy and uncommon polymorphs Titanium dioxide occurs in nature as the minerals rutile and anatase. Additionally two high-pressure forms are known minerals: a monoclinic baddeleyite-like form known as akaogiite, and the other has a slight monoclinic distortion of the orthorhombic α-PbO2 structure and is known as riesite, both of which can be found at the Ries crater in Bavaria.Akaogiite. mindat.org It is mainly sourced from 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 .
Titanium dioxide has twelve known polymorphs – in addition to rutile, anatase, brookite, akaogiite and riesite, three metastable phases can be produced synthetically (monoclinic, tetragonal, and orthorhombic ramsdellite-like), and four high-pressure forms (α-PbO2-like, cotunnite-like, orthorhombic OI, and cubic phases) also exist:
Form Crystal system Synthesis Rutile Tetragonal Anatase Tetragonal Brookite Orthorhombic TiO2(B) Monoclinic Hydrolysis of K2Ti4O9 followed by heating TiO2(H), hollandite-like formTetragonal Oxidation of the related potassium titanate bronze, K0.25TiO2 TiO2(R), ramsdellite-like form Orthorhombic Oxidation of the related lithium titanate bronze Li0.5TiO2 TiO2(II)-(α-PbO2-like form) Orthorhombic Akaogiite (baddeleyite-like form, 7 coordinated Ti) Monoclinic TiO2 -OIOrthorhombic Cubic form Cubic P > 40 GPa, T > 1600 °C TiO2 -OII, cotunnite(PbCl2)-likeOrthorhombic P > 40 GPa, T > 700 °C
The cotunnite-type phase was claimed to be the hardest known oxide with the Vickers hardness of 38 GPa and the bulk modulus of 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure. 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) and bulk modulus (~300 GPa).
Titanium dioxide (B) is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite. TiO2 also forms lamellae in other minerals.
Production
The largest pigment processors are Chemours, Venator, , and Tronox. Major paint and coating company end users for pigment grade titanium dioxide include Akzo Nobel, PPG Industries, Sherwin Williams, BASF, and Kansai Paints.Hayes (2011), p. 3 World pigment capacity was estimated at 9.9 million tonnes per year in 2025, of which China accounted for 6.0 million tonnes.
The production method depends on the feedstock. In addition to ores, other feedstocks include upgraded slag. Both the chloride process and the sulfate process (both described below) produce titanium dioxide pigment in the rutile crystal form, but the sulfate process can be adjusted to produce the anatase form. Anatase, being softer, is used in fiber and paper applications. The sulfate process is run as a batch process; the chloride process is run as a continuous process.
Chloride process
In chloride process, the ore is treated with chlorine and carbon to give titanium tetrachloride, a volatile liquid that is further purified by distillation. The TiCl4 is treated with oxygen to regenerate chlorine and produce the titanium dioxide.
Sulfate process
In the sulfate process, ilmenite is treated with sulfuric acid to extract iron(II) sulfate pentahydrate. This process requires concentrated ilmenite (45–60% TiO2) or pretreated feedstocks as a suitable source of titanium. The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise.
Examples of plants using the sulfate process are the Sorel-Tracy plant of QIT-Fer et Titane and the Eramet Titanium & Iron smelter in Tyssedal Norway.
Becher process
The Becher process is another method for the production of synthetic rutile from ilmenite. It first oxidizes the ilmenite as a means to separate the iron component.
Specialized methods For specialty applications, TiO2 films are prepared by various specialized chemistries. Sol-gel routes involve the hydrolysis of titanium alkoxides such as titanium ethoxide:
Ti(OEt)4 + 2 H2O → TiO2 + 4 EtOH
A related approach that also relies on molecular precursors involves chemical vapor deposition. In this method, the alkoxide is volatilized and then decomposed on contact with a hot surface:
Ti(OEt)4 → TiO2 + 2 Et2O
Applications
Pigment
First mass-produced in 1916, titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index, in which it is surpassed only by a few other materials (see list of indices of refraction). Titanium dioxide crystal size is ideally around 220 nm (measured by electron microscope) to optimize the maximum reflection of visible light. Approximately 4.6 million tons of pigmentary TiO2 are used annually worldwide, and this number is expected to increase as use continues to rise.
TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, toners, foods, supplements, medicines (i.e. pills and tablets), and most toothpastes; in 2019, it was present in two-thirds of toothpastes on the French market. In paint, it may be called "brilliant white", "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.
Food additive Often used as color in food, it is commonly found in ice creams, chocolates, all types of candy, creamers, desserts, marshmallows, chewing gum, pastries, spreads, dressings, cakes, some cheeses, and many other foods. It is permitted in many countries, but was banned for use in food by the European Union in 2022.
Thin films When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors; it is also used in generating decorative thin films such as found in "mystic fire topaz".
Some grades of modified titanium based pigments as used in sparkly paints, plastics, finishes and cosmetics – these are man-made pigments whose particles have two or more layers of various oxides – often titanium dioxide, iron oxide or alumina – in order to have glittering, iridescent and or pearlescent effects similar to crushed mica or guanine-based products. In addition to these effects a limited colour change is possible in certain formulations depending on how and at which angle the finished product is illuminated and the thickness of the oxide layer in the pigment particle; one or more colours appear by reflection while the other tones appear due to interference of the transparent titanium dioxide layers. In some products, the layer of titanium dioxide is grown in conjunction with iron oxide by calcination of titanium salts (sulfates, chlorates) around 800 °C One example of a pearlescent pigment is Iriodin, based on mica coated with titanium dioxide or iron (III) oxide.
The iridescent effect in these titanium oxide particles is unlike the opaque effect obtained with usual ground titanium oxide pigment obtained by mining, in which case only a certain diameter of the particle is considered and the effect is due only to scattering.
Sunscreen and UV blocking pigments In cosmetic and skin care products, titanium dioxide is used as a pigment, sunscreen and a thickener. As a sunscreen, ultrafine TiO2 is used in combination with ultrafine zinc oxide, to lower the incidence of sun burns and minimize the premature photoaging, photocarcinogenesis and immunosuppression associated with long term excess sun exposure. Sometimes these UV blockers are combined with iron oxide pigments in sunscreen to increase visible light protection.
is used extensively in plastics and other applications as a white pigment or an opacifier and for its UV resistant properties where the powder disperses light – unlike organic UV absorbers – and reduces UV damage, due mostly to the particle's high refractive index.Polymers, Light and the Science of TiO2 , DuPont, pp. 1–2
Other uses of titanium dioxide In ceramic glazes, titanium dioxide acts as an opacifier and seeds crystal formation.
It is used as a tattoo pigment and in styptic pencils. Titanium dioxide is produced in varying particle sizes which are both oil and water dispersible, and in certain grades for the cosmetic industry. It is also a common ingredient in toothpaste.
The exterior of the Saturn V rocket was painted with titanium dioxide; this later allowed astronomers to determine that J002E3 was likely the S-IVB stage from Apollo 12 and not an asteroid.
Titanium dioxide is an n-type semiconductor and is used in dye-sensitized solar cells. It is also used in other electronics components such as electrodes in batteries.
Research Patenting activities
Between 2002 and 2022, there were 459 patent families that describe the production of titanium dioxide from ilmenite. The majority of these patents describe pre-treatment processes, such as using smelting and magnetic separation to increase titanium concentration in low-grade ores, leading to titanium concentrates or slags. Other patents describe processes to obtain titanium dioxide, either by a direct hydrometallurgical process or through the main industrial production processes, the sulfate process and the chloride process. The sulfate process represents 40% of the world's titanium dioxide production and is protected in 23% of patent families. The chloride process is only mentioned in 8% of patent families, although it provides 60% of the worldwide industrial production of titanium dioxide.